feat: engagement close-session wires vault, metrics, Kai ledger (WP-0009 T09)

Add close_session helpers and CLI to append vault session logs, engagement-
scoped metrics, duty Kai charges, and client reports. Rejects sensitive
summaries. Pilot smoke-closed once; prepare points operators at close-session.

engagements/pilots/eng-coulomb-railiance01-ho-001/.kaizen/metrics/host-operator/executions.jsonl

@@ -0,0 +1 @@
+{"agent": "host-operator", "duty": "standard_review", "engagement_id": "eng-coulomb-railiance01-ho-001", "execution_time_s": 5.0, "phase": "staffing", "quality_score": 0.7, "success": true, "timestamp": "2026-07-16T10:08:57Z"}

engagements/pilots/eng-coulomb-railiance01-ho-001/.kaizen/metrics/host-operator/summary.json

@@ -0,0 +1,12 @@
+{
+  "agent": "host-operator",
+  "avg_execution_time_s": 5.0,
+  "avg_quality_score": 0.7,
+  "execution_count": 1,
+  "last_execution": "2026-07-16T10:08:57Z",
+  "success_rate": 1.0,
+  "trend": {
+    "quality_score": "stable",
+    "success_rate": "stable"
+  }
+}

engagements/pilots/eng-coulomb-railiance01-ho-001/commercial/ledger.jsonl

@@ -1 +1,2 @@
 {"apiVersion":"kaizen.agentic/v1","kind":"KaiLedgerEntry","id":"kai-20260716-quote-open","account":"coulomb-ops-kai","engagement_id":"eng-coulomb-railiance01-ho-001","type":"note","product":"quote_snapshot","capability_tier":4,"amount_kai":0,"currency":"KAI","created_at":"2026-07-16T08:00:00Z","metadata":{"total_quoted_kai":72800,"phase":"staffing","note":"Month-1 estimate recorded; no charge until fund/ramp"}}
+{"access_surcharge_product": "read_only", "account": "coulomb-ops-kai", "amount_kai": 1600, "apiVersion": "kaizen.agentic/v1", "capability_tier": 4, "created_at": "2026-07-16T10:08:57Z", "currency": "KAI", "engagement_id": "eng-coulomb-railiance01-ho-001", "id": "kai-20260716T100857Z-standard_review", "kind": "KaiLedgerEntry", "metadata": {"access_class": "read_only", "phase": "staffing", "success": true, "target": "railiance01"}, "product": "standard_review", "session_ref": "reports/2026-07-16-standard-review.md", "type": "duty_charge"}

engagements/pilots/eng-coulomb-railiance01-ho-001/reports/2026-07-16-standard-review.md

@@ -0,0 +1,13 @@
+# Session report — eng-coulomb-railiance01-ho-001
+
+- **Date:** 2026-07-16
+- **Duty:** standard_review
+- **Targets:** railiance01
+- **Outcome:** success
+- **Phase:** staffing
+
+## Summary
+
+T09 wire-up smoke: prepare+close-session path verified (no host access)
+
+_Billing metadata only in commercial/ledger.jsonl; no secrets in this report._

engagements/pilots/eng-coulomb-railiance01-ho-001/vault/memory.md

@@ -2,8 +2,8 @@
 agent: host-operator
 engagement_id: eng-coulomb-railiance01-ho-001
 project: coulomb-railiance01
-last_updated: "2026-07-16"
-session_count: 0
+last_updated: '2026-07-16'
+session_count: 1
 confidentiality: client_owned
 ---
 
@@ -72,3 +72,4 @@ _None yet._
 ## Session Log
 
 <!-- YYYY-MM-DD · host(s) · key finding · outcome -->
+- 2026-07-16 · railiance01 · standard_review · T09 wire-up smoke: prepare+close-session path verified (no host access) · ok