observability: rule-25 alerts/tile/catalog for pool-reaper metrics (#44 follow-up)

[mastermanas805]

Rule-25 monitoring follow-up for the two hot-pool reaper metrics added by provisioner PR #44 (sweep #8) in provisioner/internal/pool/metrics.go. Each metric ships its full rule-25 set in this one PR: Prom rule + NR alert JSON + dashboard tile + METRICS-CATALOG row.

instant_pool_reap_total{resource_type, status, outcome} — CounterVec

Reaper actions on status="failed" pool_items; outcome ∈ {reaped, deprovision_err, delete_err}.

• Prom rule PoolReapErrors (new group instant-provisioner-pool-reaper): rate(...{outcome=~"deprovision_err|delete_err"}[15m]) by (resource_type,outcome) > 0 for 30m, P2 warning (reaper wedged → 'failed' pool infra accumulating).
• NR alert newrelic/alerts/pool-reap-errors.json (NRQL sum over the error outcomes, FACET resource_type/outcome, WARNING > 0 / 30m).
• Dashboard tile "Pool reaper — actions by status/outcome (24h)".
• METRICS-CATALOG.md row.

instant_pool_stuck_assigned{resource_type} — GaugeVec

pool_items stuck assigned past the 30m grace. Operator signal — deliberately NOT auto-reaped (provisioner can't distinguish a crashed-claim orphan from a live api binding; truehomie-db DROP incident class).

• Prom rule PoolStuckAssigned (same group): max(...) by (resource_type) > 0 for 1h, P2 operator-action warning (leaked shared infra → manual resources-table anti-join).
• NR alert newrelic/alerts/pool-stuck-assigned.json (NRQL latest, FACET resource_type, WARNING > 0 / 1h, LAST_VALUE fill).
• Dashboard tile "Pool items stuck 'assigned' past 30m — leaked shared infra (must be 0)".
• METRICS-CATALOG.md row.

Notes / deviations from brief

• The brief suggested outcome="error" for the reap alert; the actual code emits deprovision_err and delete_err, so the rule/alert match those real label values.
• Both alerts are WARNING (P2) per rule 25 (observability/recoverable, not data-loss).

Validation

• Both new alert JSONs and the dashboard JSON parse with json.load.
• k8s/prometheus-rules.yaml parses as YAML; new group exposes PoolReapErrors + PoolStuckAssigned.
• METRICS-CATALOG table rows keep the 7-column shape.
• Dashboard edited surgically (compact one-line layout style preserved); 40 → 42 widgets.

🤖 Generated with Claude Code