feat(identity): rename user-visible identity to voculinux with one-time legacy import

The fork takes its own name everywhere a user can see it: binaries
(voculinux, voculinux-gui), desktop entry, autostart, tray, D-Bus
namespace (com.voculinux.Voculinux, no alias for the old name),
config/data/cache dirs, single-instance lock, IBus engine identity,
tray icons, resource prefixes, VOCULINUX_* environment names, and the
update-checker user agent. The internal Python module stays vocalinux
and the distribution metadata keeps the upstream URLs as provenance.

On first run a previous Vocalinux install's config.json, custom
dictionary, and portal restore token are copied once into the new
locations (new config always wins, no merge, no write-back); models
re-resolve through the pinned-checksum download path. An offline
naming-sweep test proves no old-name strings remain on user-visible
surfaces outside the allowlist.

Refs #18

scripts/generate-model-checksums.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 """Regenerate src/vocalinux/utils/model_checksums.txt from upstream metadata.
 
-Vocalinux downloads 40MB-2GB speech models at install time and on first run,
+Voculinux downloads 40MB-2GB speech models at install time and on first run,
 then hands them to native code (whisper.cpp loads its ggml files through
 ``ctypes.cdll``). Nothing about that is safe unless we know what we received,
 so every downloader checks the file against a hash pinned *in this repository*
@@ -46,7 +46,7 @@ from typing import Iterable, NamedTuple
 
 REPO_ROOT = Path(__file__).resolve().parents[1]
 SRC = REPO_ROOT / "src"
-MANIFEST = SRC / "vocalinux" / "utils" / "model_checksums.txt"
+MANIFEST = SRC / "voculinux" / "utils" / "model_checksums.txt"
 
 HF_REPO = "ggerganov/whisper.cpp"
 HF_API = f"https://huggingface.co/api/models/{HF_REPO}?blobs=true"
@@ -65,7 +65,7 @@ class Entry(NamedTuple):
 
 
 def _fetch_json(url: str):
-    request = urllib.request.Request(url, headers={"User-Agent": "vocalinux-checksum-generator"})
+    request = urllib.request.Request(url, headers={"User-Agent": "voculinux-checksum-generator"})
     with urllib.request.urlopen(request, timeout=TIMEOUT) as response:  # noqa: S310
         return json.load(response)
 
@@ -93,7 +93,7 @@ def _download_and_hash(url: str, expected_md5: str) -> tuple[str, int]:
     for rather than pinning either one.
     """
     sha256, md5, size = hashlib.sha256(), hashlib.md5(), 0
-    request = urllib.request.Request(url, headers={"User-Agent": "vocalinux-checksum-generator"})
+    request = urllib.request.Request(url, headers={"User-Agent": "voculinux-checksum-generator"})
     with urllib.request.urlopen(request, timeout=TIMEOUT) as response:  # noqa: S310
         for chunk in iter(lambda: response.read(1024 * 1024), b""):
             sha256.update(chunk)
@@ -306,7 +306,7 @@ def _vosk_entries(wanted: Iterable[str], refresh: bool) -> list[Entry]:
 def _render(entries: list[Entry], revision: str) -> str:
     width = max(len(entry.filename) for entry in entries)
     lines = [
-        "# Checksums for every speech model Vocalinux downloads.",
+        "# Checksums for every speech model Voculinux downloads.",
         "#",
         "# Generated by scripts/generate-model-checksums.py -- do not edit by hand.",
         "# Regenerate with `just model-checksums` after adding a model to",