fix: clear stale CSS properties and subtitle state on style/media update

- Remove CSS properties absent from subsequent subtitle style updates
- Broadcast subtitle:set clear when media path changes
- Preserve launcher lifecycle ownership for already-managed overlay apps
- Clamp negative autoplay current time to zero
- Reject blank subminerBinaryPath values via parseNonEmptyString
- Log and rethrow legacy config migration errors instead of swallowing
- Normalize modifier aliases (e.g. CommandOrControl) in keybinding display

src/config/service.ts

@@ -151,8 +151,9 @@ export class ConfigService {
       }
       fs.writeFileSync(configPath, content, 'utf-8');
       return rawConfig;
-    } catch {
-      return config;
+    } catch (error) {
+      console.error(`[ConfigService] legacy config migration failed for ${configPath}:`, error);
+      throw error;
     }
   }
 }