docs: generate agent-readable Swift SDK documentation

[bbbbzzzzcc-afk]

Closes wild-edge/wildedge-swift#6.

Summary

• generate a Sourcey API site from the public declarations in
  wild-edge/wildedge-swift, pinned to commit
  bf96ab894d83b72884dc8d44a065a36d1c5f0376
• publish llms.txt and llms-full.txt at the documentation root with
  absolute links to setup, API reference, output metadata, queue behavior,
  and examples
• add a Swift SDK navigation entry to the existing VitePress site
• validate that the generated site contains at least 15 public declarations,
  project-owned URLs, and pinned source links

Why

The issue asks for an agent-readable index that stays in sync with the SDK.
The build now extracts the SDK's public Swift declarations at a fixed commit,
turns them into source-mapped Markdown, and lets Sourcey publish the navigable
HTML and machine-readable indexes as part of the existing documentation build.
The output therefore changes only when the pinned SDK commit is deliberately
updated.

No WildEdge SDK runtime code is changed.

Verification

npm ci
npm run build
npm run validate:swift-api

Local validation result:

Validated 204 declarations, 11 pages, 215 pinned source links, and
project-root llms.txt outputs.

HTTP smoke tests returned 200 for /, /llms.txt, /swift-api/, the API
overview, and the generated CoreTypes reference page. The root llms.txt
was served as text/plain.

[bbbbzzzzcc-afk]

Hi @piotrekno1 — this contribution is ready for review. The documentation build and validation pass, and the change is limited to the generated Swift API documentation and its publishing support. I am happy to adjust the scope or split the change if that would make review easier.