fix(store): update_plugin silently did nothing for four installed plugins (#536)

install_plugin() deliberately renames a plugin's directory to the MANIFEST id
when it differs from the REGISTRY id, so registry `stocks` lands in
`ledmatrix-stocks/`. Every lookup in _find_plugin_path() is by directory name,
so update_plugin("stocks") found nothing, logged "Plugin not installed", and
returned False.

Nothing surfaced that to the user. Clicking update in the web UI was a no-op
with no error, and the plugin stayed on a stale version indefinitely. Four
installed plugins hit this on a real device -- leaderboard, music, stocks and
weather -- found because a scripted update of eleven plugins failed on exactly
those four.

Adds a manifest-id scan as the LAST step of the resolution chain, so the two
documented lookups above it (configured dir, then the sibling plugins/
fallback) keep their exact meaning and ordering. That ordering is pinned by
test_discovery_path_contract.py, which characterises the divergence between
the three resolvers on purpose; this extends the chain rather than reordering
it. Directories renamed aside with '.standalone-backup-' during an install or
rollback are skipped, since matching one would report a half-finished install
as a live plugin.

Also adds scripts/audit_render_path.py, which walks the call graph from
display() and reports blocking calls reachable from it. display() runs on the
render thread, so anything slow there stalls the panel; on a vsync-paced loop
a single 15ms call drops a frame and a network round trip freezes the marquee.
Two instances were already found the slow way, by reading frame-time
histograms -- odds-ticker reading the scoreboard cache per frame, and
soccer-scoreboard timing out inside update(). The audit finds that shape in
the source instead. It is a heuristic and says so: a hit behind an interval
check may be fine.

It currently flags 23 calls across six plugins. The clearest is
ledmatrix-music, whose display() falls back to an inline
requests.get(timeout=5) when album art has not been prefetched -- a deliberate
"show the art rather than go blank" tradeoff by its author, but up to five
seconds of frozen panel. Reported, not changed; that is its owner's call.

185 store tests pass. Three of the six new tests fail without the fix.

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

test/test_discovery_path_contract.py

@@ -116,6 +116,77 @@ class TestFallbackDivergence:
             plugin_dir / "config_schema.json"
 
 
+class TestRegistryIdVersusDirectoryName:
+    """install_plugin() renames a plugin's directory to the MANIFEST id when it
+    differs from the REGISTRY id, so `stocks` in the registry lands in
+    `ledmatrix-stocks/`. Every path lookup is by directory name, so
+    update_plugin("stocks") used to find nothing and report the plugin as not
+    installed -- silently. Four installed plugins hit this in practice
+    (leaderboard, music, stocks, weather): the user clicks update, nothing
+    happens, no error, and they stay on a stale version indefinitely.
+    """
+
+    def test_resolves_a_plugin_whose_directory_name_differs_from_its_id(self, tmp_path):
+        configured = tmp_path / "plugin-repos"
+        configured.mkdir()
+        plugin_dir = _write_plugin(configured, "stocks", dir_name="ledmatrix-stocks")
+
+        store = PluginStoreManager(plugins_dir=str(configured))
+        assert store._find_plugin_path("stocks") == plugin_dir
+
+    def test_direct_directory_hit_still_wins(self, tmp_path):
+        """The manifest scan is a last resort. A directory named for the id
+        must still be preferred, so the two documented lookups above keep
+        their exact meaning."""
+        configured = tmp_path / "plugin-repos"
+        configured.mkdir()
+        direct = _write_plugin(configured, "demo", dir_name="demo")
+        # A second directory whose manifest claims the same id.
+        _write_plugin(configured, "demo", dir_name="zz-other-demo")
+
+        store = PluginStoreManager(plugins_dir=str(configured))
+        assert store._find_plugin_path("demo") == direct
+
+    def test_unknown_id_is_still_not_found(self, tmp_path):
+        configured = tmp_path / "plugin-repos"
+        configured.mkdir()
+        _write_plugin(configured, "stocks", dir_name="ledmatrix-stocks")
+
+        store = PluginStoreManager(plugins_dir=str(configured))
+        assert store._find_plugin_path("no-such-plugin") is None
+
+    def test_half_finished_installs_are_not_resurrected(self, tmp_path):
+        """A directory renamed aside during install/rollback carries a valid
+        manifest. Matching one would report a ghost plugin as installed."""
+        configured = tmp_path / "plugin-repos"
+        configured.mkdir()
+        _write_plugin(configured, "ghost",
+                      dir_name="ghost.standalone-backup-1234")
+
+        store = PluginStoreManager(plugins_dir=str(configured))
+        assert store._find_plugin_path("ghost") is None
+
+    def test_unreadable_manifest_does_not_break_the_scan(self, tmp_path):
+        configured = tmp_path / "plugin-repos"
+        configured.mkdir()
+        broken = configured / "broken-plugin"
+        broken.mkdir()
+        (broken / "manifest.json").write_text("{ not json")
+        wanted = _write_plugin(configured, "stocks", dir_name="ledmatrix-stocks")
+
+        store = PluginStoreManager(plugins_dir=str(configured))
+        assert store._find_plugin_path("stocks") == wanted
+
+    def test_sibling_plugins_dir_is_searched_too(self, tmp_path):
+        configured = tmp_path / "plugin-repos"
+        configured.mkdir()
+        legacy = _write_plugin(tmp_path / "plugins", "weather",
+                               dir_name="ledmatrix-weather")
+
+        store = PluginStoreManager(plugins_dir=str(configured))
+        assert store._find_plugin_path("weather") == legacy
+
+
 class TestStandaloneBackupContract:
     def test_discovery_skips_backup_dirs(self, tmp_path):
         plugins_dir = tmp_path / "plugins"