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/files.py

@@ -0,0 +1,57 @@
+"""
+Read/write the Inara identity markdown files.
+Only whitelisted filenames are accessible — no path traversal possible.
+"""
+from fastapi import APIRouter, HTTPException
+from pydantic import BaseModel
+from config import settings
+
+router = APIRouter()
+
+ALLOWED = {
+    "SOUL.md",
+    "IDENTITY.md",
+    "USER.md",
+    "MEMORY.md",
+    "PROTOCOLS.md",
+    "CONTEXT_TIERS.md",
+}
+
+
+def _path(filename: str):
+    if filename not in ALLOWED:
+        raise HTTPException(status_code=404, detail=f"File not found: {filename}")
+    return settings.inara_path() / filename
+
+
+@router.get("/files")
+async def list_files() -> dict:
+    inara_dir = settings.inara_path()
+    files = []
+    for name in sorted(ALLOWED):
+        p = inara_dir / name
+        files.append({
+            "name": name,
+            "exists": p.exists(),
+            "size": p.stat().st_size if p.exists() else 0,
+        })
+    return {"files": files}
+
+
+@router.get("/files/{filename}")
+async def get_file(filename: str) -> dict:
+    p = _path(filename)
+    if not p.exists():
+        raise HTTPException(status_code=404, detail=f"{filename} does not exist")
+    return {"name": filename, "content": p.read_text()}
+
+
+class FileWrite(BaseModel):
+    content: str
+
+
+@router.put("/files/{filename}")
+async def save_file(filename: str, req: FileWrite) -> dict:
+    p = _path(filename)
+    p.write_text(req.content)
+    return {"ok": True, "name": filename, "size": len(req.content)}