research(binary): prototype versioned record reader

[LimiNode]

Summary

• define a non-public, versioned, big-endian framed binary record format for research
• add a bounded reader prototype with explicit bad-magic, version, flags, truncation, field, and frame errors
• cover round-trip records, multi-frame streams, and corruption/compatibility cases
• document the decision in ADR 0008 and keep production binary persistence/backends deferred

Verification

• C++11 Release build: binary_log_record_codec_test passes
• ctest --test-dir build-exec-research-cxx11 -C Release --output-on-failure -R binary_log_record_codec_test