[mvilacad]

Closes #625

Change

packages/ui/scripts/build-manifest.ts (1719 lines) is split into packages/ui/scripts/manifest/{ast,components,demos,exports,guides,paths,styling,tokens,writers}.ts; build-manifest.ts is now the 139-line orchestrator and keeps re-exporting the public types. Pure move: no logic change.

Evidence: generated outputs are byte-identical

bun run --cwd packages/ui manifest -- --skill run with origin/main's generator and with this branch's, then every output copied and compared (diff -r empty, 1173 files: the 11 dist/*.json, dist/MIGRATION.md, MIGRATION.md, skill API.md and DEMOS.md, site/public/api/v1/**, site/public/gallery/*.md):

before: 1173 files   after: 1173 files
diff -r /tmp/man-before /tmp/man-after  -> no output (BYTE-IDENTICAL)
sha256 of all (path-sorted file hashes): 7f0278b0c0a7fdfdc8394321e40a82895aae293df77dedec55a5024556cae452 (both)

Checklist

• bun run validate passes (pre-push)
• No published-package change (dev script), so no changeset