feat(ui): add a desktop panel rail to each sidebar

Each side stack hosts a Vue rail listing its panels; selecting one opens it
through PanelChrome. The shell owns one Vue runtime and Pinia instance, and a
panel store mirrors each side's panels from the DOM. The rail hides with its
stack, in Cockpit, clean view and recording, and on phones. Panels without a
catalog entry get a generic item, and Data Layers leaves the rail while the
f shortcut hides it.

src/i18n/locales/ja.json

@@ -2873,5 +2873,7 @@
   "Load scenes from an exported JSON file": "書き出したJSONファイルからシーンを読み込む",
   "Download the timing log of the last play": "前回の再生のタイミングログをダウンロード",
   "Edit anchors, data packs and shot details": "アンカー、データパック、ショットの詳細を編集",
-  "Download this scene as JSON or an asset bundle": "このシーンをJSONまたはアセットバンドルとしてダウンロード"
+  "Download this scene as JSON or an asset bundle": "このシーンをJSONまたはアセットバンドルとしてダウンロード",
+  "Left panels": "左パネル",
+  "Right panels": "右パネル"
 }