chore(build): uv tooling, a Python 3.11 floor, and verified model downloads (epic #701, phases 2.5 & 5) (#713)

* chore(build): migrate justfile tooling to uv

All recipes now run through 'uv run' against .venv, with a shared
DEV_EXTRAS variable (dev + vad) because uv syncs the environment
exactly and would otherwise uninstall the dev tools between
recipes. 'deps' installs dev+vad; new 'deps-all' covers every
extra. 'build' switches to 'uv build'; 'version' uses --no-sync.

Bump [tool.uv] required-version to >=0.12,<0.13 for uv 0.12.x, and
raise the mypy python_version target to 3.12: mypy 1.19 in the lock
cannot target 3.9 and numpy 2.x stubs need a 3.12 target to parse
(mypy is not run in CI or pre-commit; this only affects 'just
typecheck').

* fix(tests): isolate test runs from real XDG state; fix Arch model-path crash

Local test runs failed en masse (185 failures) while CI stayed
green: tests picked up the developer's real ~/.local/share/vocalinux
models via the default XDG paths and switched IBus/keyboard code
paths through the desktop session env (XDG_CURRENT_DESKTOP/
XDG_SESSION_TYPE on GNOME/Wayland, issue #478 branches). conftest
now points XDG base dirs at a throwaway session-wide directory and
clears session variables at import time, mirroring a fresh CI
runner (paths like MODELS_DIR freeze at first import during
collection, so fixture-time isolation is too late).

Also guard the Arch branch of _get_system_model_paths(): it removed
/usr/local/share/vocalinux/models unconditionally and crashed with
ValueError on Arch hosts when a custom XDG_DATA_DIRS never added
that path. Add regression tests, and make the lock-file test assert
the actual $XDG_DATA_HOME/vocalinux contract instead of the
hardcoded ~/.local/share default.

* fix(tests): keep the IBus engine double a plain class

Python 3.14's unittest.mock re-instantiates a user subclass when it builds
child mocks (klass(name=...)). VocalinuxEngine inherits from whatever
IBus.Engine resolves to, and the test module bound that to the MagicMock
class itself, so every engine instantiation raised

    TypeError: VocalinuxEngine.__init__() got an unexpected keyword argument 'name'

on 3.14 while passing on 3.13. Replace it with a plain stand-in class that
still hands out per-instance MagicMocks for the IBus API surface the engine
touches.

The same pattern remains in test_ibus_engine.py, test_ibus_engine_utils.py,
test_ibus_active_engine_guard.py and test_ibus_xkb_wayland.py; those never
instantiate the engine, so they are unaffected for now.

* fix(install): build the venv from the system Python

install.sh looked up a bare `python3` from PATH. Started from an activated
virtualenv — a shell left in uv's .venv after `just deps` — it built venv/
from that interpreter, where distro PyGObject is invisible even with
--system-site-packages, and the run aborted with

    Distro PyGObject (python3-gi / python3-gobject) is not importable in the venv.

A mismatched venv/ then survived every retry, because the installer reuses
whatever venv it finds.

- drop an inherited VIRTUAL_ENV (and its bin from PATH) before any
  interpreter lookup
- select the interpreter explicitly: $SYSTEM_PYTHON (default
  /usr/bin/python3) or PATH python3, preferring one that can import gi,
  and create the venv with it instead of `python3`
- recreate venv/ when it was built by a different interpreter
- name the interpreter in the PyGObject guard's error

Documents the two environments (uv's .venv for tooling, venv/ for the
installed app) in CONTRIBUTING, the justfile header and AGENTS.md, and adds
the mismatch symptom to the INSTALL troubleshooting section.

* chore(python): raise the supported floor to 3.11

requires-python promised 3.9 while the CI matrix ran 3.9/3.10/3.11/3.13,
the classifiers advertised up to 3.14, mypy targeted 3.12 and install.sh
enforced 3.9 — five different answers to "which Python does this support".

Settle on 3.11 everywhere: pyproject (requires-python, classifiers, black
targets), install.sh's MIN_VERSION, check-system-deps.sh, the distro package
map, the CI matrix (now 3.11-3.14, matching the classifiers), the release and
nightly workflows, and the docs.

mypy now targets the floor instead of 3.12, so type checking covers what we
promise; numpy 2.x ships stubs in 3.12 syntax that a 3.11 target cannot
parse, so its imports are skipped. (mypy has 71 pre-existing errors either
way; no CI job gates on it.)

uv.lock and the requirements/* exports are regenerated — dropping 3.9/3.10
removes most of the version-conditional resolution branches.

tests/test_python_version_policy.py pins the invariant: install.sh's floor,
requires-python, the classifiers and the CI matrix must agree.

* ci: run lint and tests from uv.lock

The lock file and the hash-pinned exports were not enforced anywhere: CI
still built a venv by hand and installed unpinned `PyGObject` plus
`-e ".[dev,vad]"`, so the tool versions it checked against had nothing to do
with the ones `just lint` uses locally.

Both Python jobs now use astral-sh/setup-uv and run through `uv sync
--locked` / `uv run --locked`, which also fails the build when uv.lock drifts
from pyproject.toml.

Partially covers phase 5 of #701 (tests install from the lock, lock freshness
gate); trusted publishing, artifact checksums and action SHA pinning are
still open there.

* ci: lint from a dedicated dependency group

The lint job failed on this branch: `uv run --extra dev` syncs the whole
project, so it tried to build pyaudio from source on a runner that installs
no system dependencies.

    src/pyaudio/device_api.c:9:10: fatal error: portaudio.h: No such file or directory

Move black/isort/flake8 out of the `dev` extra into a `lint` dependency
group. CI runs `uv run --locked --only-group lint`, which installs the three
pure-Python tools and skips the project entirely — no portaudio or
girepository headers needed. `just deps` and DEV_EXTRAS request the group
alongside the dev extras, so the local environment still carries test and
lint tooling at once and `just lint` matches CI version for version.

pre-commit is unaffected: its hooks pin their own tool versions upstream.

* fix(install): never configure an engine the venv cannot import

vosk became an optional extra in #705, but the installer still writes
`"engine": "vosk"` into config.json on the whisper.cpp fallback path even
when installing the extra only produced a warning. config.json also survives
reinstalls — every writer guards on "file does not exist" — so an engine
picked by an earlier attempt outlives the venv that supported it. Either way
Vocalinux dies at startup:

    ModuleNotFoundError: No module named 'vosk'

- the fallback now writes the vosk config only when `import vosk` actually
  succeeds, and otherwise leaves the engine configuration alone
- a new verify_configured_engine() runs near the end of the install: if
  config.json selects vosk and the venv cannot import it, it says so and
  prints both fixes instead of leaving a broken install behind

* feat(models): verify every model download against a pinned digest

Pins a sha256/md5 per downloadable speech model in
src/vocalinux/utils/model_checksums.txt and verifies against it in both
install.sh and the runtime downloaders, before the file is moved into place.
Verification fails closed. Covers phase 2.5 of #701; see the PR for details.

* docs(agents): rebase AGENTS.md onto the #727 rewrite

* fix(install): hash models that are already on disk instead of trusting them

* refactor(models): one download path per engine, and fix Whisper's

* docs(install): drop distros that cannot meet the 3.11 floor

* docs: retire the distros and Python versions the 3.11 floor rules out

* fix(install): abort instead of warning when Python is below the floor

* fix(install): fall back to the system Python, not the one on PATH

* fix(install): match an existing venv by installation, not by X.Y

* fix(install): repair a config naming an engine the venv cannot import

* fix(models): pin VOSK by the sha256 of bytes we fetched, not upstream's md5

* fix(justfile): request the dev set in every recipe that syncs

* test(version): scan the docs and website trees for a stale Python floor

* docs: correct the stale model-checksum and distro claims

* fix(models): stamp the VOSK tree the app extracts, as the installer does

* fix(install): replace an unverified VOSK model only once its successor is ready

* docs(install): align the Fedora floor with the rest of the tree

* test(install): drop an f-string with no placeholders

* test(models): stub the downloader probe the VOSK installer test relies on

* docs: drop the long dashes from two model-checksum comments

* fix(install): gate on the interpreter, not on the distro release label

* fix(justfile): export the lint group into requirements/dev.txt

* fix(models): unpack the VOSK tree into staging and stamp it before the swap

* fix(whisper): adopt a checkpoint an earlier release stored under the catalog name

* docs(settings): state what a stray Whisper copy really means for deletion

* fix(models): hash a whisper.cpp model found on disk before it reaches ctypes

* docs(contributing): stop telling readers to uninstall their linters

* fix(install): stop warning off distros the project documents as supported

* docs(distros): file the supported derivatives under supported

.github/workflows/distro-test-matrix.yml

@@ -28,8 +28,8 @@ jobs:
       fail-fast: false
       matrix:
         container:
-          - ubuntu:22.04
           - ubuntu:24.04
+          - ubuntu:26.04
           - debian:12
           - fedora:39
     container:
@@ -268,8 +268,8 @@ jobs:
           echo "Check individual job logs for details."
           echo ""
           echo "Expected behavior:"
-          echo "  ✓ ubuntu:22.04 - Full support expected"
           echo "  ✓ ubuntu:24.04 - Full support expected"
+          echo "  ✓ ubuntu:26.04 - Full support expected"
           echo "  ✓ debian:12 - Full support expected"
           echo "  ⚠ fedora:39 - Good support, minor differences expected"
           echo ""

.github/workflows/nightly.yml

@@ -26,7 +26,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: '3.10'
+          python-version: '3.11'
           cache: 'pip'
 
       - name: Install system dependencies
@@ -213,7 +213,7 @@ jobs:
           | **Version** | ${{ steps.version.outputs.version }} |
           | **Base Version** | ${{ steps.version.outputs.base_version }} |
           | **Build Date** | ${{ steps.version.outputs.date }} |
-          | **Python** | 3.9+ |
+          | **Python** | 3.11+ |
           | **OS** | Linux (X11 & Wayland) |
 
           ---
@@ -284,7 +284,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: '3.10'
+          python-version: '3.11'
           cache: 'pip'
 
       - name: Install system dependencies

.github/workflows/release.yml

@@ -11,7 +11,8 @@ permissions:
   id-token: write  # Required for PyPI trusted publishing
 
 env:
-  PYTHON_VERSION: '3.10'
+  # Build against the supported floor (requires-python in pyproject.toml).
+  PYTHON_VERSION: '3.11'
 
 jobs:
   build-and-release:

.github/workflows/unified-pipeline.yml

@@ -70,28 +70,26 @@ jobs:
     steps:
       - uses: actions/checkout@v5
 
-      - name: Set up Python
-        uses: actions/setup-python@v5
+      - name: Set up uv
+        uses: astral-sh/setup-uv@v6
         with:
-          python-version: '3.13'
-          cache: 'pip'
-
-      - name: Install linting tools
-        run: |
-          python -m pip install --upgrade pip
-          pip install flake8 "black>=26,<27" isort
+          enable-cache: true
 
+      # --only-group lint installs the linters without the project itself, so
+      # this job needs no portaudio/girepository headers to build pyaudio and
+      # PyGObject. --locked fails if uv.lock drifts from pyproject.toml, so the
+      # tool versions are the ones `just lint` uses locally.
       - name: Lint with flake8 (critical errors)
         run: |
-          flake8 src/ tests/ --count --select=E9,F63,F7,F82 --show-source --statistics
+          uv run --locked --only-group lint flake8 src/ tests/ --count --select=E9,F63,F7,F82 --show-source --statistics
 
       - name: Check formatting with black
         run: |
-          black --check --diff src/ tests/
+          uv run --locked --only-group lint black --check --diff src/ tests/
 
       - name: Check import sorting with isort
         run: |
-          isort --check-only --diff --profile black src/ tests/
+          uv run --locked --only-group lint isort --check-only --diff --profile black src/ tests/
 
   python-test:
     name: 🧪 Test Python ${{ matrix.python-version }}
@@ -102,16 +100,18 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ['3.9', '3.10', '3.11', '3.13']
+        # Every version requires-python promises; keep in sync with the
+        # classifiers in pyproject.toml (tests/test_python_version_policy.py).
+        python-version: ['3.11', '3.12', '3.13', '3.14']
 
     steps:
       - uses: actions/checkout@v5
 
-      - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v5
+      - name: Set up uv
+        uses: astral-sh/setup-uv@v6
         with:
+          enable-cache: true
           python-version: ${{ matrix.python-version }}
-          cache: 'pip'
 
       - name: Install system dependencies
         run: |
@@ -136,24 +136,18 @@ jobs:
           # Alternatively, for older Ubuntu versions (like 22.04), you might need:
           # sudo apt-get install -y libgirepository1.0-dev pkg-config
 
-      - name: Set up virtual environment
-        run: |
-          python -m venv venv
-          source venv/bin/activate
-          python -m pip install --upgrade pip setuptools wheel
-          # Install PyGObject from pip (with build deps installed above)
-          pip install PyGObject
-          pip install -e ".[dev,vad]"
-          echo "VIRTUAL_ENV=$VIRTUAL_ENV" >> $GITHUB_ENV
-          echo "PATH=$VIRTUAL_ENV/bin:$PATH" >> $GITHUB_ENV
+      # PyGObject is built from the lock here: the runner has glib 2.80+ and the
+      # -dev headers installed above. End users get the distro package instead
+      # (install.sh builds venv/ with --system-site-packages).
+      - name: Install dependencies from uv.lock
+        run: uv sync --locked --extra dev --extra vad
 
       - name: Run tests with coverage
         run: |
-          source venv/bin/activate
           # Set GI_TYPELIB_PATH so pip-installed PyGObject can find system typelibs (AppIndicator3, etc.)
           # Use dynamic detection for cross-distro compatibility, fallback to common Ubuntu paths
           export GI_TYPELIB_PATH=$(pkg-config --variable=typelibdir gobject-introspection-1.0 2>/dev/null || echo "/usr/lib/x86_64-linux-gnu/girepository-1.0:/usr/lib/girepository-1.0")
-          PYTHONPATH=$PWD pytest --junitxml=junit-${{ matrix.python-version }}.xml --cov=src --cov-report=xml tests/
+          PYTHONPATH=$PWD uv run --locked --extra dev --extra vad pytest --junitxml=junit-${{ matrix.python-version }}.xml --cov=src --cov-report=xml tests/
 
       - name: Upload test results
         if: always()
@@ -163,7 +157,7 @@ jobs:
           path: junit-${{ matrix.python-version }}.xml
 
       - name: Upload coverage to Codecov
-        if: matrix.python-version == '3.10'
+        if: matrix.python-version == '3.13'
         uses: codecov/codecov-action@v4
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
@@ -189,7 +183,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: '3.10'
+          python-version: '3.11'
           cache: 'pip'
 
       - name: Install system dependencies