Improve API reference navigation and changelog

[SandroMaglione]

Summary

• generate a changelog page from released and pending Changesets, including tag-derived release dates when available
• expose declaration-level navigation in module tables of contents and make Pagefind results link directly to matching APIs
• support concise, highlighted changelog code examples, document the release-note style, and improve the 0.7.0 entry
• add focused generator coverage and fetch complete tag history in the Pages build

Changeset

• Added or updated for a library or package-metadata change
• Not required because this PR does not change src/ or package.json

Validation

• pnpm check
• Relevant example checks, when examples changed
• Automated type-performance measurement passed or was not required
• Automated runtime- and memory-performance measurement passed or was not required

The generated site was also checked locally for changelog layout, inline and fenced code rendering, collapsible declaration navigation, and exact API search scrolling.