fix(local-qa): harden Host-Worker protocol

[wanghuan-520]

Closes #5954

Summary

• harden the fixed Worker process with bounded frames, strict sequencing, clean EOF, and sanitized protocol failures
• add shared Rust/TypeScript negative conformance fixtures and cross-field reference/timestamp validation
• restore registry, lockfile, rustfmt, scaffold, and Worker CI coverage after github-devloop implementation for #5956 #5964
• keep Host integration, Chrome launch, and Evidence storage out of scope

Verification

• TypeScript qa-contracts tests/build pass
• Rust qa-contracts tests pass
• Worker build and 25 process/policy tests pass
• Local QA fmt/clippy/build pass
• Local QA workspace tests pass excluding existing real Chrome integration test, which fails on this macOS environment during process-group cleanup with EPERM

🤖 Generated with Claude Code