feat: add epoch-start scheduled dogfood measurement

[cafitac]

Summary

• Add --epoch-start to dogfood trace-quality so trace-quality can measure an explicit fresh epoch boundary instead of only a relative lookback window.
• Propagate --epoch-start through dogfood scheduled-dry-run so scheduled readiness bundles can avoid legacy lookback pollution while staying read-only.
• Add regression coverage and update .dev status/roadmap docs with the v0.1.154 continuation evidence.

Live/source evidence

• /Users/reddit/.agent-memory/reports/v0.1.154-continuation-20260513T120215/trace-quality-epoch-start-repo.json
• /Users/reddit/.agent-memory/reports/v0.1.154-continuation-20260513T120215/scheduled-dry-run-epoch-start-repo.json

Safety

• Read-only/reporting only.
• No broad G4/background apply support added.
• No default ranking migration, telemetry reset, ordinary conversation auto-approval, or collapse/delete apply enabled.

Tests

• uv run --python 3.11 pytest tests/ -q
• uv run --python 3.11 pytest tests/test_roadmap_contract.py tests/test_cli.py::test_python_module_cli_dogfood_trace_quality_epoch_start_filters_legacy_rows tests/test_cli.py::test_python_module_cli_dogfood_scheduled_dry_run_bundles_read_only_reports_without_leaks -q