feat: engine/model in audit log + docs update

- tool_audit: ContextVars (engine, model) set at orchestrator run start; fields added to every entry
- orchestrator_engine: tool_audit.set_context("gemini", model_name) at run() start
- openai_orchestrator: tool_audit.set_context("openai", model label) at run() start
- audit table: Model column between Status and Args
- HELP.md: push notifications section, audit log in Files section, tool count 30→40, new API endpoints
- TODO__Agents.md: web_push and audit log marked complete with full detail

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

documentation/TODO__Agents.md

@@ -39,8 +39,7 @@ New tools for `cortex/tools/` — higher-value additions that fill obvious gaps.
 - [x] **`file_write`** — overwrite/append to home_root paths, admin-only, confirm-required — 2026-04-29
 - [x] **`nc_talk_send`** — outbound NC Talk message via notification.py, admin-only — 2026-04-29
 - [x] **`email_send`** — SMTP via email_utils, per-user regex allowlist in `home/{user}/email_allowlist.json`, managed via Settings UI textarea + Files panel raw editor — 2026-04-29
-- [ ] **`web_push`** — send a browser push notification (requires push subscription stored
-      per-user; pairs well with the PWA service worker already in place)
+- [x] **`web_push`** — VAPID push via pywebpush; subscriptions in `home/{user}/push_subscriptions.json`; "Enable notifications" toggle in ☰ menu; sw.js push+notificationclick handlers — 2026-05-05
 
 ### [Channel] Proactive notifications
 Inara reaches out on her own initiative via NC Talk or Google Chat when a reminder
@@ -121,6 +120,15 @@ so Scott can see who's spending what.
 - [ ] Expose via `/api/usage` endpoint; add a summary row to the Settings page
 - [ ] Optional: soft spending limit with a warning toast when exceeded
 
+### [Security] Tool call audit log — 2026-05-05
+Every orchestrator tool invocation logged to `home/{user}/tool_audit/YYYY-MM-DD.jsonl`.
+- [x] `tool_audit.py` — JSONL writer with asyncio locks; ContextVars for engine/model set by each orchestrator at run start
+- [x] Hook in `call_tool()` — fire-and-forget `asyncio.create_task`; captures status ok/error/denied, 300-char result snippet, args (truncated at 500 chars)
+- [x] `GET /api/audit/files` — lists available dates for current user (self-service)
+- [x] `GET /api/audit/day?date=` — returns entries for one date (self-service)
+- [x] `GET /api/audit/recent` + `/stats` — cross-user aggregation (admin only)
+- [x] "Audit Log" group in Files panel sidebar (collapsed by default) — read-only table with time/tool/status/model/args/result columns; colour-coded status
+
 ### [Intelligence] Dev agent pipeline
 See `ARCH__Intelligence_Layer.md`. Full design not yet started.
 - [ ] Specialist agent: frontend (SvelteKit) code changes