docs: sync content with recent library and dashboard changes

[cursor]

Summary

• add complete Google Drive integration docs for the shipped Dashboard workflow, including current access modes and Translate / Apply changes / Retranslate behavior
• document Next.js automatic JSX injection constraints and the newly shipped shared config types
• correct post-refactor blog links, a hard getGT 404, a broken deploy anchor, and the unavailable sitemap claim
• clean recently introduced frontmatter whitespace

Findings by severity

• Broken: hard getGT 404, broken Next.js deploy target, and advertised /sitemap.md endpoint returning 404
• Wrong: SPA-only automatic JSX claim, stale/misdirected blog links, undocumented Google Drive workflow, and incomplete config-spread typing docs
• Polish: trailing spaces in three recently touched titles

Verification

• pnpm build:content (436 generated pages)
• node --experimental-strip-types scripts/validate-links.ts
• node --experimental-strip-types scripts/validate-unsafe-html.ts
• fresh Next.js 16.2.10 project with published gt-next@11.0.10 and @generaltranslation/compiler@1.3.32: webpack injection confirmed; Turbopack skip warning confirmed
• published generaltranslation@9.0.3 and gt-node@1.0.7 config type exports type-checked