feat(overlay): add subtitle selection modal and Jellyfin 12 fixes

- Add an optional subtitle selection modal for primary/secondary mpv tracks (subtitleSelection.enabled, g-s sequence shortcut) with key-sequence conflict handling
- Authenticate Jellyfin URLs with the ApiKey query, answer remote keep-alives, clear now-playing on stop, and restore episode titles in Anki misc info
- Honor the configured mpv executable when Jellyfin starts playback via a shared mpv-process launcher
- Bump electron-builder to 26.16.1
- Condense and reconcile changelog fragments; update config example and docs

docs-site/public/config.example.jsonc

@@ -22,6 +22,15 @@
     "externalHostManagementUrl": "" // Docker host management URL for automatic character dictionary uploads and replacement. Empty disables external uploads.
   }, // Configure the linked Docker host management URL, for example http://127.0.0.1:8780.
 
+  // ==========================================
+  // Subtitle Selection
+  // Select primary and secondary mpv subtitle tracks from the overlay.
+  // Hot-reload: enabling or disabling updates the session shortcut immediately.
+  // ==========================================
+  "subtitleSelection": {
+    "enabled": false // Use the SubMiner modal to select primary and secondary subtitle tracks. When enabled, its shortcut overrides mpv subtitle selection. Values: true | false
+  }, // Select primary and secondary mpv subtitle tracks from the overlay.
+
   // ==========================================
   // Japanese Subtitle Generation
   // Generate timed Japanese subtitles from local audio using whisper.cpp.
@@ -239,6 +248,7 @@
     "openRuntimeOptions": "CommandOrControl+Shift+O", // Accelerator that opens the runtime options modal.
     "openJimaku": "Ctrl+Shift+J", // Accelerator that opens the Jimaku subtitle search modal.
     "openTsukihime": "Ctrl+Shift+T", // Accelerator that opens the TsukiHime subtitle search modal (configured secondary/Japanese primary tabs).
+    "openSubtitleSelection": "g-s", // Open subtitle selection when enabled. Use g-s to press g then s. Set null to unbind.
     "openSubtitleGeneration": "Ctrl+Shift+G", // Accelerator that opens the standalone Japanese subtitle generation modal.
     "openSessionHelp": "CommandOrControl+Slash", // Accelerator that opens the session help / keybinding cheatsheet.
     "openControllerSelect": "Alt+C", // Accelerator that opens the controller selection and learn-mode modal.