chore: release v0.2.1

ci: add GitHub Release + MCP Registry publish to workflow

Adds version-already-published check, GitHub Release creation,
and mcp-publisher OIDC auth for Official MCP Registry.

Initial release: Pagecast — record any browser page as GIF or video v…

…ia MCP

Powered by Playwright + ffmpeg. 6 MCP tools:
- record_page, interact_page, stop_recording
- convert_to_gif (two-pass palette), record_and_gif, list_recordings

Features: headed by default, session-based multi-recording,
lazy browser launch, optimized GIF output.

Co-Authored-By: Claude Opus 4.6 <[email protected]>