(orchestration): Track bypass events for automated review gates

## Component

API or orchestration

## Describe the feature

When repos enable automated pre-human review, record **break-glass bypass** events when a human or policy override merges or advances a PR without automated approval. Feed counts into evaluation dashboards to tune reviewer strictness.

## Use case

Automated reviewers only improve if operators measure when humans **disagree** with them. Without bypass telemetry, teams over-tighten or under-tighten rules based on anecdotes.

## Proposed solution

1. GitHub webhook handler detects merge/approve without required check (when check integration exists) or manual CLI `bgagent review bypass --reason`.
2. Persist `review_bypass` events with reason, actor, finding IDs dismissed.
3. Surface in `bgagent stats` and roadmap analytics widgets.

## Other information

- Depends on **feature-pre-human-automated-review-gate** or customer branch protection wiring; can ship CLI-only bypass logging first.
- Privacy: store finding categories, not full diffs, in event payload.

## Acknowledgements

- [ ] I may be able to implement this feature
- [ ] This might be a breaking change

## Acceptance criteria

- [ ] Bypass events written to `TaskEvents` with structured schema.
- [ ] Operator can list bypasses per repo for a time window via API or CLI.
- [ ] Documentation explains how bypass rate should influence policy tuning.
- [ ] Tests cover webhook and CLI bypass paths.

Inizia con il gestore del webhook GitHub, il comando manuale di bgagent per ignorare la revisione e lo schema TaskEvents menzionato nell’issue. Traccia il percorso degli eventi fino alle statistiche di bgagent e ai widget di analisi della roadmap, quindi esamina i test esistenti per webhook e CLI. Il lavoro è completo quando è possibile registrare ed elencare eventi strutturati di bypass per repository e intervallo temporale, con copertura per entrambi i percorsi e documentazione per la messa a punto delle policy.

Scritto dal modello di indicizzazione a partire dal testo della issue.