test: add same-evidence reader quality eval case

[Stahl-G]

Summary

• add packaged public-safe eval case same_evidence_reader_quality_regression
• add eval runner action quality.summarize to write Quality Panel JSON, summary, and HTML for fixture validation
• document the same-evidence regression boundary in evaluation-case docs and changelog

Boundary

• deterministic regression guard only
• no subagent execution, source fetching, model-quality score, semantic proof, delivery approval, or release authority
• fixture uses synthetic ExampleCo evidence and reader-safe output

Validation

• python3 -m pytest -q tests/test_evaluation_cases.py
• PYTHONPATH=src python3 -m multi_agent_brief.cli.main eval-cases validate --json
• PYTHONPATH=src python3 -m multi_agent_brief.cli.main eval-cases run --case-id same_evidence_reader_quality_regression --repo-workdir . --json
• python3 -m pytest -q tests/test_evaluation_cases.py tests/test_quality_panel.py tests/test_materiality_selection.py tests/test_support_wording.py tests/test_status.py
• python3 scripts/check_release_consistency.py --no-tag
• python3 scripts/check_product_baseline.py
• python3 scripts/check_briefloop_skill_freshness.py
• python3 scripts/check_skill_contract.py
• python3 scripts/check_version_consistency.py
• PYTHONPATH=src python3 scripts/check_capabilities.py
• python3 scripts/check_runtime_asset_parity.py
• python3 scripts/generate_agent_configs.py --check
• python3 scripts/sync_hermes_plugin_skills.py --check
• git diff --check
• python3 -m compileall -q src tests
• python3 -m pytest -q