Add CLAUDE.md guide for Claude Code sessions

[anshmudgil]

Summary

Adds a root CLAUDE.md so future Claude Code sessions have a compact, authoritative guide to the codebase.

Distills agent-relevant essentials:

• Overview — single-process FastAPI + asyncio runtime wrapping the Claude Agent SDK; personal vs worker mode.
• Commands — uv setup, pytest, web build/lint/dev, nerve lifecycle. Verified against pyproject.toml, web/package.json, .github/workflows/ci.yml.
• Layout — backend subsystems under nerve/ mapped to one-liners.
• Conventions & gotchas — Python 3.13 floor + memu-py pin, _env first-import, DB migration pattern, config merge, .env/secrets.
• Docs — pointer to docs/ for depth.

Single-file additive change. No code touched.

🤖 Generated with Claude Code

[CLAassistant]

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