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_appimage_packaging.py

@@ -113,7 +113,7 @@ def test_running_from_appimage_follows_appdir(monkeypatch):
 
     monkeypatch.delenv("APPDIR", raising=False)
     assert not running_from_appimage()
-    monkeypatch.setenv("APPDIR", "/tmp/.mount_vocalinux")
+    monkeypatch.setenv("APPDIR", "/tmp/.mount_voculinux")
     assert running_from_appimage()
 
 
@@ -185,8 +185,8 @@ def test_appimage_build_rebuilds_pywhispercpp_with_vulkan():
     text = BUILD_SH.read_text()
     assert "GGML_VULKAN=1" in text
     assert "libggml-vulkan" in text
-    assert "VOCALINUX_APPIMAGE_REQUIRE_VULKAN" in text
-    assert "VOCALINUX_APPIMAGE_SKIP_VULKAN" in text
+    assert "VOCULINUX_APPIMAGE_REQUIRE_VULKAN" in text
+    assert "VOCULINUX_APPIMAGE_SKIP_VULKAN" in text
     assert "rebuild_pywhispercpp_vulkan" in text
     assert 'CC="${CC:-gcc}"' in text
     assert 'CXX="${CXX:-g++}"' in text
@@ -345,7 +345,7 @@ def test_vulkan_shaders_get_the_compiler_the_base_image_lacks():
     for workflow in APPIMAGE_WORKFLOWS:
         content = (WORKFLOWS / workflow).read_text(encoding="utf-8")
         assert (
-            "vocalinux-appimage" in content
+            "voculinux-appimage" in content
         ), f"{workflow} does not cache the built glslc; every run rebuilds it"