feat: Thinking indicator + cancel button in the app

- Bridge: _emit_activity() spiegelt OpenClaw agent events als agent_activity
  an RVS, dedupliziert State-Wechsel. chat:final/error senden idle.
- Bridge: Neuer cancel_request-Handler ruft Diagnostic /api/cancel per HTTP.
- Diagnostic: Neuer POST /api/cancel Endpoint (gleiche Logik wie WS-Cancel).
- RVS: agent_activity + cancel_request in ALLOWED_TYPES.
- App: Gelber Indicator ueber der Input-Bar mit Text je nach Activity,
  roter Abbrechen-Button. Cancel sendet cancel_request via RVS.
- issue.md: Erledigte Bugfixes + Features konsolidiert.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

rvs/server.js

@@ -16,6 +16,7 @@ const ALLOWED_TYPES = new Set([
   "file_request", "file_response", "file_saved", "stt_result", "config", "tts_request",
   "xtts_request", "xtts_response", "xtts_list_voices", "xtts_voices_list", "voice_upload", "xtts_voice_saved",
   "update_check", "update_available", "update_download", "update_data",
+  "agent_activity", "cancel_request",
 ]);
 
 // Token-Raum: token -> { clients: Set<ws> }