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_update_checker.py

@@ -114,7 +114,7 @@ class TestTrustedUrls:
     def test_rejects_untrusted_urls(self):
         assert not is_trusted_release_url("https://evil.example/payload")
         assert not is_trusted_release_url("http://github.com/VocaHQ/vocalinux")
-        assert not is_trusted_release_url("https://github.com/evil/vocalinux")
+        assert not is_trusted_release_url("https://github.com/evil/voculinux")
         assert not is_trusted_release_url("")
 
 
@@ -315,7 +315,7 @@ class TestFetchLatestRelease:
     def test_evil_update_url_does_not_become_html_url(self, caplog):
         tag_url = "https://github.com/VocaHQ/vocalinux/releases/tag/v0.17.0"
         evil_paths = [
-            "/evil/vocalinux/releases/tag/v9",
+            "/evil/voculinux/releases/tag/v9",
             "https://evil.example/x",
             "/VocaHQ/vocalinux/releases/../evil",
         ]
@@ -343,7 +343,7 @@ class TestFetchLatestRelease:
         }
         untrusted_urls = (
             "https://evil.example/VocaHQ/vocalinux/releases/tag/v0.17.0",
-            "https://github.com/evil/vocalinux/releases/tag/v0.17.0",
+            "https://github.com/evil/voculinux/releases/tag/v0.17.0",
             "http://github.com/VocaHQ/vocalinux/releases/tag/v0.17.0",
         )
         caplog.set_level(logging.WARNING, logger="vocalinux.utils.update_checker")
@@ -392,11 +392,11 @@ class TestFetchLatestRelease:
         first, second = mock_requests.get.call_args_list
         assert first[0][0] == "https://api.github.com/repos/VocaHQ/vocalinux/releases/latest"
         assert first.kwargs["headers"]["Accept"] == "application/vnd.github+json"
-        assert first.kwargs["headers"]["User-Agent"] == "Vocalinux-UpdateChecker"
+        assert first.kwargs["headers"]["User-Agent"] == "Voculinux-UpdateChecker"
         assert "Authorization" not in first.kwargs["headers"]
         assert second[0][0] == "https://github.com/VocaHQ/vocalinux/releases/latest"
         assert second.kwargs["headers"]["Accept"] == "application/json"
-        assert second.kwargs["headers"]["User-Agent"] == "Vocalinux-UpdateChecker"
+        assert second.kwargs["headers"]["User-Agent"] == "Voculinux-UpdateChecker"
         assert "Authorization" not in second.kwargs["headers"]
         assert fallback.url == tag_url
         assert _checker_warnings(caplog) == []