Keyboard-first Direct review foundation

[kvkenyon]

Summary

• harden feedback submission against moved symbolic heads at the store/HTTP boundary
• replace scattered shortcuts with a typed command registry, roving focus, quick find, contextual help, palette, and input/IME-safe keyboard handling
• replace modal line comments with recoverable inline exact-anchor drafts and add accessible diff-line names/navigation
• add pre-paint Light/Dark/System themes and responsive neo-brutalist tokens with all review actions retained at narrow widths and 400% zoom
• add large/long-path fixtures, bounded measurement helpers, documented baselines, and the approved additive future protocol direction

Validation

• npm run check
• npm run test:e2e
• Chrome DevTools AXI inspection of the packed loopback product and network
• npm run fixture:large && npm run measure:baseline

Phase 2 scalable protocol work, Guided generation, and loopback model integration are intentionally out of scope.