fix(v0.7.64): highlight the homepage nav link and truncate collapsed changelog titles

[qiansc]

Summary

• The knowledge website homepage no longer highlights the first section in the top bar. A site.nav link to the current page, such as a position: "start" documentation home link, is highlighted instead; the server-rendered active class is kept for origin links.
• Changelog cards show the title on one line, truncated, while collapsed, and wrap the full title when expanded. Grid columns use minmax(0, 1fr) so long titles no longer widen the page.
• Bump all packages to 0.7.64 and document the homepage highlight rule in Package Outputs.

Validation

• packageSite, siteTranslation, indexerGuideResources and pluginPromptMigration tests
• bun run typecheck, bun run build, bun run release:prepare
• Local preview of the documentation site homepage and changelog in light and dark