Add source-linked API reference

[mossony]

Summary

• add a Sourcey 3.6.5 API reference that indexes 24 public symbols across 11 Python source files
• generate four focused reference pages plus an introduction, search index, and LLM context exports
• pin every API entry to an immutable GitHub source line and expose the exact package version and source commit
• validate and deploy the site at the repository-owned GitHub Pages path with GitHub Actions

Why

The README gives concise usage examples, but the package does not currently have a browsable API reference. This keeps the README focused while making validation, signing, data-model, exception, and optional FastAPI APIs searchable and source-linked.

Impact

This is documentation-only and does not change the Python package or runtime behavior. The reference is regenerated from the source before every build. After merge, a maintainer needs to select GitHub Actions as the Pages source once; subsequent pushes to main deploy automatically.

Validation

• npm run check --prefix docs
• python3 -m pytest -q — 38 passed
• browser QA at the production /telegram-init-data/ base path on desktop and a 390×844 viewport
• verified navigation, search-to-anchor behavior, line-level source links, and zero browser console errors

Prepared with OpenAI Codex; I reviewed the generated reference and ran the checks above.