Add benchmark evidence replay dashboard

[ictechgy]

Summary

• add context-guard-bench --evidence-jsonl replay mode and --dashboard-md rendering
• keep CSV schema unchanged while annotating replay/public-claim provenance in reports and ledgers
• add synthetic 12-task replay evidence fixture plus docs/package/test coverage

Validation

• python3 scripts/sync_plugin_copies.py --check
• python3 -m py_compile context-guard-kit/benchmark_runner.py plugins/context-guard/bin/context-guard-bench tests/test_context_guard_kit.py
• PYTHONDONTWRITEBYTECODE=1 python3 -m unittest tests.test_context_guard_kit.BenchmarkRunnerTests
• PYTHONDONTWRITEBYTECODE=1 python3 scripts/prepublish_check.py --skip-tests
• python3 scripts/release_smoke.py --timeout 20
• PYTHONDONTWRITEBYTECODE=1 python3 scripts/prepublish_check.py

Claim boundary: synthetic/manual replay evidence is not public hosted API token/cost savings evidence; provider-export provenance plus matched-task quality/token/cost gates remain required.

[ictechgy]

G001 quad review loop completed for R2.

Review verdicts:

• Codex: APPROVE — prior provider_export public-claim blocker resolved; no CRITICAL/HIGH/MEDIUM blockers.
• Claude: APPROVE — report-level eligibility now requires same-run completeness, provider-export provenance, raw savings status, and matched-pair claim boundaries.
• Forge: APPROVE — no CRITICAL/HIGH/MEDIUM blockers.
• Agy: APPROVE — no eligibility-gate blocker found after short re-run.

Validation evidence:

• python3 scripts/sync_plugin_copies.py --check
• python3 -m py_compile context-guard-kit/benchmark_runner.py plugins/context-guard/bin/context-guard-bench tests/test_context_guard_kit.py
• PYTHONDONTWRITEBYTECODE=1 python3 -m unittest tests.test_context_guard_kit.BenchmarkRunnerTests
• PYTHONDONTWRITEBYTECODE=1 python3 scripts/prepublish_check.py --skip-tests
• python3 scripts/release_smoke.py --timeout 20
• PYTHONDONTWRITEBYTECODE=1 python3 scripts/prepublish_check.py
• GitHub CI: test-and-prepublish on 3.11, 3.12, macos-latest/3.12 all SUCCESS.

Proceeding to merge.