Shrink README to a concise product overview (capabilities, quick start, build,
test, structure, doc links). Move API reference, types, JSON schemas, and CLI
detail to docs/API.md; move error catalogue to docs/ERRORS.md; move pipeline
layers to docs/ARCHITECTURE.md. Add CLAUDE.md with README policy and sync task.
Add STATUS.md (what's done, verification, future work), GITEA.md (act_runner,
master branch policy, pipeline), and CONTRIBUTING.md (dev guide, new language
checklist). Update README for all 28 validators, docs index, and project tree.
Align Gitea Actions with master as default branch; add PR and issue templates.
Expand .gitignore for debug artifacts and test binaries.
