feat: tool call audit log

Every orchestrator tool invocation is recorded to home/{user}/tool_audit/YYYY-MM-DD.jsonl.
Each entry captures: timestamp, user, tool, args (truncated), status (ok/error/denied),
result length, and a 300-char result snippet.

- tool_audit.py: JSONL writer with per-file asyncio locks; read_recent / read_recent_all_users helpers
- tools/__init__.py: hook in call_tool() — fire-and-forget record on every dispatch
- routers/audit.py: GET /api/audit/recent and /api/audit/stats (admin-only)
- tools/files.py: add home_root() to file_read allowed roots so agents can read audit JSONL

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

cortex/main.py

@@ -9,7 +9,7 @@ logging.basicConfig(level=logging.INFO, format="%(levelname)s:%(name)s: %(messag
 from config import settings
 from auth_middleware import SessionAuthMiddleware
 from routers import chat, google_chat, nextcloud_talk, files, distill, auth, orchestrator
-from routers import ui, onboarding, settings, help, auth_google, local_llm, push
+from routers import ui, onboarding, settings, help, auth_google, local_llm, push, audit
 
 
 @asynccontextmanager
@@ -35,6 +35,7 @@ app.include_router(distill.router)
 app.include_router(auth.router)
 app.include_router(orchestrator.router)
 app.include_router(push.router)
+app.include_router(audit.router)
 
 # Static files — must be mounted BEFORE ui.router so /static/* is matched first.
 # ui.router has a wildcard /{username}/{persona} that would otherwise catch /static/style.css etc.