feat: audit log, usage tracking UI, OpenAI orchestrator compaction, onboarding + docs

Tool audit log:
- Every orchestrator tool call logged to home/{user}/tool_audit/YYYY-MM-DD.jsonl
- Files panel sidebar: audit log group (collapsed), date-linked read-only table
- Admin endpoints: /api/audit/files, /api/audit/day, /api/audit/recent, /api/audit/stats
- Engine and model name recorded per entry

OpenAI orchestrator improvements:
- Context budget enforcement: 75% of model context_k (min 16k)
- Message compaction: truncates old tool results when approaching budget
- max_rounds respected per model config (intersected with server cap)

OpenRouter onboarding (setup.html, onboarding.py, app.js, settings.html):
- Step 3 of 3: /setup/model with curated model picker
- Chat banner for users on server-default model (informational, not alarmist)
- Settings quick-link card; /setup/model works standalone for existing users

Model registry + session store:
- set_role_config / get_role_config for per-role tool lists and system_append
- session_store: session rename, session name backfill endpoint

UI updates (app.js, index.html, style.css, local_llm.html):
- Role toggle in context panel
- Off-the-record mode
- Agent notes read-only viewer
- OPERATIONS.md loaded at T2+ in context

Documentation:
- HELP.md: full tool table, per-role tool sets, Agent Notes, usage tracking
- TOOLS.md: Agent Notes section, count corrected to 44
- ARCH__SYSTEM.md, ARCH__BACKENDS.md, MASTER.md updated to match reality
- CLAUDE.md: onboarding flow, documentation philosophy sections
- README.md: stack in practice, DeepSeek TUI mention, architecture diagram updated
- TODO__Agents.md: onboarding task completed with deviation notes

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

cortex/static/TOOLS.md

@@ -1,6 +1,6 @@
 # Tool Reference
 
-> This reference covers all 40 orchestrator tools available when the ⚡ toggle is on.
+> This reference covers all 44 orchestrator tools available when the ⚡ toggle is on.
 > Tools are invoked automatically by the orchestrator — you don't call them directly.
 
 ¹ **Admin only** — requires the `admin` role. Invisible to regular users.  
@@ -102,3 +102,14 @@
 | Tool | What it does |
 |---|---|
 | `ae_task_list` ¹ | List tasks from the agents_sync Kanban board |
+
+## Agent Notes
+
+Private, durable notes visible only to the orchestrator — not surfaced to users. Persist across sessions. Only available in orchestrated (tool-enabled) sessions.
+
+| Tool | What it does |
+|---|---|
+| `agent_notes_read` | Read the current private notes file |
+| `agent_notes_write` | Overwrite the notes file completely |
+| `agent_notes_append` | Append a timestamped entry (keeps last 3 backups automatically) |
+| `agent_notes_clear` | Erase all notes (backs up first) |