Docs/starlight docs

[p2arthur]

Summary

This PR migrates project documentation from the legacy TypeDoc setup to Astro Starlight, and standardizes the docs structure + publishing flow.

What Changed

• Set up a Starlight docs app in docs/ (astro.config.mjs, sidebar.config.json, content.config.ts, docs/package.json).
• Moved and reshaped docs content into docs/src/content/docs/** using MDX and a Starlight-friendly hierarchy (home, quick start, core/building/advanced concepts).
• Added starlight-typedoc integration to generate API docs into the Starlight site.
• Added static examples generation (docs/scripts/generate-examples-mdx.ts) from root examples/** with shared parsing helpers (docs/src/loaders/examples-loader.ts).
• Updated CI/CD for docs:
  • PR docs build validation (check_docs in pr.yml)
  • GitHub Pages publishing via a reusable composite action
  • DevPortal publishing workflow
  • Release workflow wired to the new docs publish flow

Impact

• Documentation is now centralized in Starlight with improved navigation and consistency.
• Docs publishing and validation are aligned with the Starlight migration workflow.
• Examples and API reference are integrated into the same docs experience.