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/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._