[iuyo5678]

Define the wire protocol for optional local pairing: bounded schema validation, canonical field encoding, HMAC proofs, rotation and recovery commit proofs, and the pairing-required error in Rust and TypeScript. Legacy unpaired business handshakes remain available in the later default policy.

Rust and Web Crypto share fixed vectors. The extension uses bounded JSON.parse and validates the same parsed value with the schema and HMAC; no custom duplicate-key scanner is retained.

Validation across the final stack:

• Rust workspace: 1,020 passed, one existing ignored; formatting and strict Clippy.
• Extension: 3,570 passed, 363 environment-dependent skips; TypeScript, Biome and production build.
• Five real-daemon tests using the current CLI and published 0.4.1; real Chrome for Testing pairing/navigation smoke.
• The 0.4.2 stage independently passed 131 focused tests, three real-daemon tests, typecheck and Biome.

Stack 1/9; base: main. Review order: #424 → #425 → #426 → #427 → #428 → #429 → #430 → #431 → #432.