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_model_checksums.py

@@ -140,7 +140,7 @@ class TestManifestCoverage(unittest.TestCase):
 class TestVerifyFile(unittest.TestCase):
     def setUp(self):
         self.tmp = Path(self.enterContext(__import__("tempfile").TemporaryDirectory()))
-        self.payload = b"vocalinux model payload"
+        self.payload = b"voculinux model payload"
         self.path = self.tmp / "model.bin"
         self.path.write_bytes(self.payload)
         self.digest = hashlib.sha256(self.payload).hexdigest()
@@ -416,7 +416,7 @@ class TestExistingModelsAreVerified(unittest.TestCase):
         for name, checker in (
             ("install_whisper_model", "verify_openai_model_checksum"),
             ("install_whispercpp_model", "verify_model_checksum"),
-            ("install_vosk_models", ".vocalinux_verified"),
+            ("install_vosk_models", ".voculinux_verified"),
         ):
             guard = self._exists_guard(name)
             self.assertLess(
@@ -484,9 +484,9 @@ print_error() { echo "ERROR: $*"; }
 print_success() { echo "SUCCESS: $*"; }
 command_exists() { command -v "$1" >/dev/null 2>&1; }
 DATA_DIR="$ROOT/data"
-VOCALINUX_TMP_DIR="$ROOT/tmp"
+VOCULINUX_TMP_DIR="$ROOT/tmp"
 MODEL_CHECKSUMS_FILE="$ROOT/model_checksums.txt"
-mkdir -p "$VOCALINUX_TMP_DIR"
+mkdir -p "$VOCULINUX_TMP_DIR"
 
 # The installer only probes for these; the download itself is stubbed out.
 check_connectivity() { return 0; }
@@ -663,8 +663,8 @@ download_model_file() { echo "DOWNLOAD ATTEMPTED"; return 1; }
         """The 40MB fetch must not happen when nothing can verify it."""
         with TemporaryDirectory() as tmp:
             result = self._run(
-                f'DATA_DIR="{tmp}/data"; VOCALINUX_TMP_DIR="{tmp}/tmp"; '
-                f'mkdir -p "$DATA_DIR" "$VOCALINUX_TMP_DIR"; '
+                f'DATA_DIR="{tmp}/data"; VOCULINUX_TMP_DIR="{tmp}/tmp"; '
+                f'mkdir -p "$DATA_DIR" "$VOCULINUX_TMP_DIR"; '
                 f'MODEL_CHECKSUMS_FILE="{tmp}/nope.txt"; '
                 "install_vosk_models; echo RC=$?",
                 functions=("pinned_digest_for", "install_vosk_models"),