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>

README.md

@@ -10,6 +10,43 @@ Cortex is a self-hosted multi-agent AI platform. It supports multiple users, eac
 
 ---
 
+## Where Cortex Fits
+
+AI tools aren't one-size-fits-all. Cortex exists in a specific niche — it's not trying to be everything.
+
+**Cortex is a self-hosted persona platform.** It gives you a persistent AI companion with its own
+identity, memory, and voice — reachable through your chat apps, not just a browser tab. It remembers
+who you are across days and weeks. It can proactively message you on a schedule. It runs on your
+own hardware, behind your own auth.
+
+### What Cortex is good at
+- **Being a consistent AI presence** — same persona, same memory, day after day
+- **Multi-channel access** — web, Nextcloud Talk, Google Chat, all routed to the same brain
+- **Proactive work** — scheduled messages, reminders, cron jobs that reach out to you
+- **Multi-user households** — each person gets their own persona (Scott → Inara, Holly → Tina)
+- **Private, offline-capable** — local models via Ollama when you don't want anything leaving the LAN
+
+### What Cortex is not
+- **Not a coding assistant.** Cortex lives in chat apps, not in your terminal or IDE.
+  Use Claude Code, DeepSeek TUI, Gemini CLI, or Copilot for code-level work — they specialize in reading and
+  editing project files. Cortex can't open a codebase.
+- **Not a generic LLM chat UI.** Open WebUI and LibreChat are excellent model-switching frontends.
+  Cortex isn't a frontend — it's a platform with its own identity system, orchestrator, and memory
+  pipeline. Two different jobs.
+- **Not a SaaS product.** Nobody else hosts your Cortex instance. Nobody else sees your conversations.
+  The trade-off is you manage the service yourself — `systemctl --user restart cortex`.
+- **Not an agent framework.** LangChain, CrewAI, and similar are libraries for building AI pipelines.
+  Cortex is a running service with concrete personas, not an abstraction layer to build on top of.
+
+### The stack in practice
+- Use **Cortex** to talk to Inara — daily assistant, memory keeper, scheduled check-ins
+- Use **Claude Code / DeepSeek TUI** to work *on* Cortex — code edits, architecture, debugging
+- Use **Open WebUI** when you want to test a new model or run a quick prompt without persona context
+
+Same AI, different interfaces for different jobs.
+
+---
+
 ## Quick Orientation
 
 | Directory | What it is |