## What changed
- Pass metrics bound to the active turn's model to approval-review contributors.
- Add counter support to `ExtensionMetrics` while preserving host session attribution.
- Record Guardian v2 tool-call score lag and count stale-score fallbacks with the `score_lag` reason.
## Testing
- Cover counter forwarding and session metadata tags.
- Verify Guardian v2 metric samples for current and stale scores.
GitOrigin-RevId: 0ec34736d29d2e37ed217a27e773b4f6230ae38a