docs: add root README, CONTRIBUTING, onboarding section, gitignore fixes
- README.md: new root README with CI badge, per-service table, quick start,
CI pipeline table, file budget docs, and links to production endpoints
- CONTRIBUTING.md: dev environment setup, pre-commit checklist, commit
marker reference, architecture non-negotiables, Claude Code section
- CLAUDE.md: insert First-Time Setup & Claude Code Onboarding section with
branch guard, hook explanation, guardrail marker table, and staging rules
- REFACTOR_PLAYBOOK.md: commit existing refactor playbook doc
- .gitignore: add dist/, .turbo/, pnpm-lock.yaml, .pnpm-store/ to prevent
SDK build artifacts from appearing as untracked files
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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