Summary

Add Skills over MCP to the Extensions website:

• An implementation overview with a brief motivation, discovery/loading flow, capability negotiation, and consistent JSON examples.
• Guidance for direct URI lookup, lazy reads, manifest verification, updates, optional directory browsing, and client/server requirements.
• A landing-page entry, navigation item, and Skills column with direct partial-support documentation links.

The overview follows the Tasks extension page and the Tools/Resources/Prompts conventions, with neutral client/server language, specification requirement terms, and labelled request/response examples.

Merge gate

Keep this PR in draft until SEP-2640 is Final: conformance tests and a reference implementation in any Tier 1 SDK must be merged. Tracking: conformance #330, Go #1238, and C# #1856. Recheck support before publishing.

Validation

• npm run prep
• git diff --check
• Checked all 16 added live link targets and their fragments; verified the new Skills-page routes locally.
• Compiled the MDX with GitHub-flavored Markdown; verified tables, request/response labels, and code blocks.
• Parsed all eight JSON examples; verified both example files' byte sizes and SHA-256 digests, frontmatter, and cross-example URIs.

Local validation uses node --import tsx; repository scripts are unchanged.

AI assistance

Codex assisted with research, documentation, review fixes, the PR description, and validation at Sambhav's request.