Context

Part of kcenon/common_system#685 (Wave 2, P1).

Acceptance Criteria

• add benchmarks/baselines/ JSON baselines + benchmark-comparison regression gate
• record per-category test pass + line/branch coverage in docs/performance/BASELINE.md
• build/test the C++20 module (.cppm) target across all CI compilers
• add a dedicated fuzz/ target for exporters/internal wire format + collectors

Notes

Benchmark/CI gates touch .github/workflows/ -> requires workflow token scope.

Derived from the 2026-05-30 multi-agent cross-system level-matching analysis (workflow wf_0a968699-e07). Reference systems: documentation=common_system, code-structure=monitoring_system, tests/examples=container_system.