Add SSE real-time Talk activity, file editor UI, and identity file API

- event_bus.py: in-process asyncio pub/sub (one Queue per SSE client)
- nextcloud_talk.py: publishes nct_message/nct_response events to bus
- chat.py: GET /events SSE endpoint streams Talk activity to browser
- routers/files.py: whitelist-protected GET/PUT for Inara identity .md files
- main.py: register files router
- static/index.html: real-time Talk feed, blue badge on Sessions btn,
  Files modal with preview/edit toggle and Ctrl+S save

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cortex/routers/chat.py

@@ -8,6 +8,7 @@ from llm_client import complete
 from session_logger import log_turn
 from session_store import load as load_session, save as save_session, list_all, generate_session_id
 from config import settings
+import event_bus
 
 
 router = APIRouter()
@@ -141,6 +142,30 @@ async def replace_history(session_id: str, req: HistoryUpdate) -> dict:
     return {"ok": True, "session_id": session_id}
 
 
+@router.get("/events")
+async def sse_events() -> StreamingResponse:
+    """Server-sent events stream — pushes real-time Talk activity to the browser."""
+    async def stream():
+        q = event_bus.subscribe()
+        try:
+            while True:
+                try:
+                    event = await asyncio.wait_for(q.get(), timeout=20)
+                    yield f"data: {json.dumps(event)}\n\n"
+                except asyncio.TimeoutError:
+                    yield 'data: {"type":"keepalive"}\n\n'
+        except (GeneratorExit, asyncio.CancelledError):
+            pass
+        finally:
+            event_bus.unsubscribe(q)
+
+    return StreamingResponse(
+        stream(),
+        media_type="text/event-stream",
+        headers={"Cache-Control": "no-cache", "X-Accel-Buffering": "no"},
+    )
+
+
 @router.post("/note")
 async def add_note(req: NoteRequest) -> dict:
     """Inject a public note into session history so the LLM sees it next turn."""