build(deps): consolidate updates and clear dependency audits

[jdevalk]

The open dependency updates overlap in their lockfiles, and the existing dependency trees contain audit findings. This combines #188, #191, #203, #202, and #201 into one tested update for the website and MCP service.

Updates Astro/MDX, DOMPurify, development tools, Workers types, and Wrangler, and refreshes compatible transitive dependencies. Regenerates the browser's vendored DOMPurify asset from the resolved 3.4.15 release. Both dependency trees now report zero npm audit vulnerabilities.

Adds a narrowly scoped Miniflare override for Sharp 0.35.4: Wrangler's bundled Miniflare otherwise pins the vulnerable 0.35.2 release. AVIF encoding and decoding passed with the patched version.

Validation on Node 22.22.3:

• Clean installs for both packages; both npm audits report zero vulnerabilities.
• Website build and integrity checks, Astro check, lint, formatting, skill validation, and WebSub tests passed. Astro check reports zero errors or warnings, with 44 existing hints.
• Internal link crawl found zero broken links (5,055 scanned; 4,826 skipped).
• Built website search, navigation from search results, and the global search overlay worked in the browser.
• MCP data generation, type checking, and Wrangler deployment dry run passed. The built bundle passed legacy and modern discovery, tool listing, search, and category smoke checks.

The five original dependency PRs can be closed after this merges. This does not include the separate MCP protocol or specification-content changes.

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