P0-4 observability closeout: remaining metrics, dashboard coverage, alert-ready signals

[krusty-agent]

Summary

• emit activity_event_total on Mission Control assignee events (action=assigned)
• emit run_control_action_total{action,result} on agent launch control actions (success + failure paths)
• emit run-health gauges from team health query:
  • agent_heartbeat_age_ms{agentSlug}
  • agent_stale_total
• expand dashboard config to include remaining implemented metrics:
  • mutation_latency_ms (p50/p95 by mutation)
  • route_view_total (rate by route)
• update observability metric catalog statuses + runbook coverage/gaps

Validation

• ✅ npm run mission-control:validate-observability
  • metric catalog uniqueness/sync checks passed
  • dashboard↔catalog metric references passed
  • alert↔routing consistency passed

Notes

• npx tsc -b --pretty false currently fails on pre-existing unrelated typegen/type errors in DID and Mission Control UI files; no new type errors introduced by this PR scope.

[krusty-agent]

Superseded by consolidated integration PR #161: #161