Native Apple implementation plan

Spec: ../specs/2026-09-13-native-apple-design.md. Independent spec review approved by agent dispatched as gpt-6-astra (high), 2026-09-13; runtime identity not independently verified. Spec approval is not branch or parity acceptance.

1. Add CRDT native mutation ABI to a separately built WASM module, maintaining the existing server ABI and artifact. Add native interpreted host wrapper with bounded calls. Verify identity-preserving Yjs round trips and UTF-16 mutations before wiring a UI.
2. Add shared proof-bound native authentication and metadata/sharing JSON endpoints using current session/admission/owner checks. Preserve store encryption and transport routes.
3. Implement Apple document projection, selection/IME-aware native editor, command catalog and clipboard/layout adapters. Bind command mutations to CRDT deltas and own-origin undo.
4. Implement native list, sharing, exports and print; use generated twelve-locale resources. Integrate shared bounded transport and SSE, retaining pending edits and surfacing failures.
5. Build Mac, iPhone/iPad simulator and device apps; test fixtures/concurrent browser editing, run web gates and independent native/branch review. Record any unmet acceptance explicitly.