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

tests/test_installer_gate.py

@@ -174,7 +174,7 @@ def test_the_gate_takes_this_commit_from_git_not_the_working_directory():
     ), "the gate no longer extracts the tree from git"
     installer = INSTALLER.read_text(encoding="utf-8").splitlines()
     assert any(
-        "grep" in line and "pyproject.toml" in line and "vocalinux" in line for line in installer
+        "grep" in line and "pyproject.toml" in line and "voculinux" in line for line in installer
     ), (
         "local mode is no longer detected from pyproject.toml in the working"
         " directory; the gate may now be testing a downloaded tag instead of"
@@ -206,9 +206,9 @@ def test_the_smoke_checks_what_the_installer_claims_to_have_created():
     gate = _gate_text()
     for construct in (
         r'\[ -x "\$VENV/bin/python" \]',
-        r'\[ -x "\$INSTALL_HOME/\.local/bin/vocalinux" \]',
-        r'\[ -f "\$INSTALL_HOME/\.local/share/applications/vocalinux\.desktop" \]',
-        r"'\$INSTALL_HOME/\.local/bin/vocalinux' --version",
+        r'\[ -x "\$INSTALL_HOME/\.local/bin/voculinux" \]',
+        r'\[ -f "\$INSTALL_HOME/\.local/share/applications/voculinux\.desktop" \]',
+        r"'\$INSTALL_HOME/\.local/bin/voculinux' --version",
     ):
         assert re.search(construct, gate), f"the smoke no longer asserts {construct}"
 
@@ -306,13 +306,13 @@ def test_the_remote_gate_bootstraps_outside_a_checkout():
     checkout exists. Overriding the clone source is what keeps the run on this
     commit instead of the public repo's last release."""
     gate = _without_comments(_remote_gate_text())
-    assert "VOCALINUX_REPO_URL" in gate, (
+    assert "VOCULINUX_REPO_URL" in gate, (
         "the remote gate no longer redirects the clone source; it would"
         " install the public repo's tag rather than this commit"
     )
     installer = _without_comments(INSTALLER.read_text(encoding="utf-8"))
-    assert re.search(r"VOCALINUX_REPO_URL:-https://github\.com/VocaHQ/vocalinux\.git", installer), (
-        "install.sh no longer honors VOCALINUX_REPO_URL; the gate's mirror"
+    assert re.search(r"VOCULINUX_REPO_URL:-https://github\.com/VocaHQ/vocalinux\.git", installer), (
+        "install.sh no longer honors VOCULINUX_REPO_URL; the gate's mirror"
         " cannot reach it and the clone falls back to the public repo"
     )
 
@@ -346,7 +346,7 @@ def test_the_remote_gate_checks_handoff_artifacts():
     gate = _without_comments(_remote_gate_text())
     for construct in (
         r'\[ -x "\$REMOTE_VENV/bin/python" \]',
-        r'\[ -f "\$INSTALL_HOME/\.local/bin/activate-vocalinux\.sh" \]',
+        r'\[ -f "\$INSTALL_HOME/\.local/bin/activate-voculinux\.sh" \]',
     ):
         assert re.search(construct, gate), f"the remote gate no longer asserts {construct}"
 
@@ -355,9 +355,9 @@ def test_the_remote_gate_smoke_tests_the_installed_app():
     """Same standard as the local gate: the app binary answers --version
     through the wrapper the user's PATH carries."""
     gate = _without_comments(_remote_gate_text())
-    assert re.search(r"'\$INSTALL_HOME/\.local/bin/vocalinux' --version", gate)
+    assert re.search(r"'\$INSTALL_HOME/\.local/bin/voculinux' --version", gate)
     assert re.search(
-        r'\[ -x "\$INSTALL_HOME/\.local/bin/vocalinux" \]', gate
+        r'\[ -x "\$INSTALL_HOME/\.local/bin/voculinux" \]', gate
     ), "the remote gate no longer asserts the user-facing wrapper exists"