Add protocol frame codec recovery tests

[fengyangxxx]

Summary

Fixes #2.

Adds deterministic protocol frame codec recovery coverage for malformed frame boundaries, and fixes the codec header-size mismatch so encoded frames can be decoded against the declared 24-byte header contract.

This PR is scoped only to the protocol frame codec recovery bounty.

Changes

• Writes the full 8-byte reserved header field so FrameEncoder matches FRAME_HEADER_SIZE = 24.
• Rejects non-zero reserved header bytes with ProtocolError::InvalidMessage.
• Tracks successfully accepted frames through FrameDecoder::accepted_frames().
• Resynchronizes the decoder to the next frame magic after malformed magic, unsupported version, and oversized payload headers so a following valid frame can still decode.
• Preserves a following valid frame after reserved-byte and checksum failures.
• Adds a dedicated protocol::frame_tests module for malformed wire-input and recovery fixtures.

Testing

• cargo test --lib
  • PASS: 32 tests.
• python3 build.py --list
  • PASS: command completed successfully.
• python3 build.py
  • Generated and committed diagnostic/build-3ce6b853.json plus diagnostic/build-3ce6b853.logd.
  • Diagnostic summary: 10 modules total, 7 passed, 3 failed.
  • Passing modules: backend, frontend, market, compliance, v2-market-stream, nfc-scanner, openapi-tools.
• git diff --check
  • PASS.

Diagnostic artifacts

• diagnostic/build-3ce6b853.json
• diagnostic/build-3ce6b853.logd

The diagnostic bundle was generated by running python3 build.py in a clean Linux container using the committed tools/encryptly/linux-x64/encryptly binary.

Notes

• The generated diagnostic password is intentionally not copied into this PR body.
• Maintainers may remove diagnostic artifacts before merging if desired.