docs: comprehensive doc audit — sync all docs to current state
- MASTER.md: tool count 40→47, add proactive notifications + spawn_agent rows, date bump
- ROADMAP.md: mark local orchestrator/web push/proactive notifs/spawn_agent/web_read/session_read as done, date bump
- ARCH__CHANNELS.md: rewrite notification channel config section — all 4 channels, all triggers, on-demand endpoints
- ARCH__SYSTEM.md: update tools/ module list to include files, agents
- README.md: update LLM backends in architecture diagram, add browser push to channels table
- CLAUDE.md: add doc update checklist to Documentation Philosophy section
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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