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/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