feat(co-host): popup UI — promote/demote, controller badges, controller-aware lock

- updateHostControlUI takes a state object now; role badge shows Host / Controller
  / Guest; remote-control lock uses amController (a co-host can drive, so their
  buttons aren't locked).
- Peer list: Host/Controller badges and, for the owner, a per-peer Give control /
  Revoke button (SET_PEER_ROLE). Shown only when the feature is active and the room
  is host-only or the viewer is the owner — no role noise for guests in normal rooms.
  Hidden entirely against a relay without the co-host capability.
- i18n: BADGE_CONTROLLER, BTN_GIVE_CONTROL, BTN_REVOKE_CONTROL across all 15 locales.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

extension/locales/ja.json

@@ -50,6 +50,9 @@
   "NOTICE_HOST_CONTROLS": "ホストが全員の再生を操作します。",
   "BADGE_HOST": "ホスト",
   "BADGE_GUEST": "ゲスト",
+  "BADGE_CONTROLLER": "操作権あり",
+  "BTN_GIVE_CONTROL": "操作権を付与",
+  "BTN_REVOKE_CONTROL": "取り消す",
   "BADGE_DESYNCED": "ソロ",
   "TOOLTIP_PEER_DESYNCED": "単独で視聴中 — ホストのコマンドを無視しています",
   "HCM_DIALOG_TITLE": "KoalaSync · ホストがこのルームを操作中",