Fix template CI registry helper deps

Goal

Make plate-template and plate-playground-template build again after the registry UI/plugin refactors added helper-file imports.

Plan

• [completed] Find which registry items are missing helper files or helper dependencies.
• [completed] Patch registry definitions so generated template installs include those files.
• [in_progress] Rebuild registry output and update local templates.
• [in_progress] Run template build verification and summarize.

Findings

• CI is failing in generated templates, not in apps/www.
• The missing modules are all helper files introduced or depended on by registry items:
  • block-discussion-index
  • get-annotation-click-target
  • suggestion-line-break-anchor
  • suggestion-styles
  • trailing-block-kit

Progress

• Loaded learnings/task/react/planning-with-files/tdd.
• Confirmed the break is in registry/template dependency wiring, not app-local imports.
• Added registry coverage for block-discussion-index, get-annotation-click-target, and trailing-block-kit.
• Inlined suggestion-line-break-anchor and suggestion-styles into ui/suggestion-node.tsx, then removed the extra registry file entries.
• Rebuilt apps/www registry output with pnpm --filter www rd.
• pnpm turbo typecheck --filter=./apps/www and pnpm lint:fix passed.
• Investigated the separate Vercel failure and reproduced it locally with pnpm turbo build --filter=./apps/www.
• The first fix used packages/core/src/react/index.ts, but pnpm brl rewrote that generated barrel and reintroduced drift.
• Moved the durable client boundary to packages/plate/src/react/index.tsx, which survives pnpm brl.
• pnpm brl and pnpm turbo build --filter=./apps/www now both pass together.