fix: recover issue loop control plane

[codeacme17]

Summary

• require UI Draft PRs to render exact-head before/after screenshots directly in the PR body
• publish inline COMMENT-only reviews through a trusted canonical JSON publisher
• restore Git credential helper operations and Docker safe-directory verification
• isolate frozen implementation contracts from issue-authored headings
• reject hidden legacy verifier sentinels

Verification

• pnpm verify: passed (exit code 0)
• issue loop tests: 92/92 passed
• structural validation: 66 protected files passed
• Nextra UI contract: 120 component and 8 localized home checks passed

Bootstrap authorization

This is a one-time owner-authored control-plane bootstrap PR because the currently installed router cannot authorize its own repair. It must remain Draft until @codeacme17 performs the final review and merge. No automation may mark it Ready, approve it, or merge it.