fix: address CodeRabbit review findings across runtime modules

- Extract filterLegacyMpvPluginFileCandidates, buildYomitanAnkiSettingsKey, setMpvCurrentSecondarySubText, runSupportAssetUpdatesForLauncherResult helpers
- Include forceOverride in yomitan anki settings cache key (was missing, causing incorrect cache hits)
- Detect same-PID stale stats daemon state to avoid self-connect
- Validate non-empty extension in buildFfmpegSubtitleExtractionArgs
- Drop unused message param from showOverlayLoadingStatusNotification
- Log and rethrow on session bindings artifact write failure
- Add unit tests for all extracted helpers

src/main/runtime/session-bindings-runtime.ts

@@ -54,7 +54,12 @@ export function createSessionBindingsRuntime(deps: SessionBindingsRuntimeDeps):
       warnings,
       numericSelectionTimeoutMs: deps.getConfiguredShortcuts().multiCopyTimeoutMs,
     });
-    writeSessionBindingsArtifact(deps.configDir, artifact);
+    try {
+      writeSessionBindingsArtifact(deps.configDir, artifact);
+    } catch (error) {
+      deps.logWarn('[session-bindings] Failed to write session bindings artifact');
+      throw error;
+    }
     deps.setSessionBindings(bindings);
     deps.setSessionBindingsInitialized(true);
     const mpvClient = deps.getMpvClient();