hub v0.40.0: store escrow restic_pw_sha256 + serve escrow status in the report ACK (SLICE 3)

Additive host_escrow migration; SaveHostEscrow/HostEscrow gain the hash
(NULL-safe for legacy rows); GetEscrowStatusForCustomer joins hosts;
the report ACK gains escrow:{identity_blob_present,restic_pw_sha256,
created_at} (omitted without a row). Contract test mirrors the agent's
v0.79.0 emit struct.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PSK5g6qYLknKj8u3QAFEr6

hub/CHANGELOG.md

@@ -1,5 +1,23 @@
 # Felhom Hub — Changelog
 
+## v0.40.0 — SLICE 3: store the escrow password-hash + serve escrow status in the report ACK (2026-07-09)
+
+The hub-verified escrow auto-confirm chain, hub third (pairs with agent v0.79.0 + controller v0.108.0).
+The controller must verify the RIGHT fact — not "a blob exists" but "the blob covers the CURRENT repo
+password" — so the hub records WHICH password each escrow covers, as a non-reversible sha256 (a 256-bit
+random secret's hash is safe to store/serve; the password itself never reaches the hub).
+
+- `internal/store`: additive migration `ALTER TABLE host_escrow ADD COLUMN restic_pw_sha256 TEXT`
+  (NULL on legacy rows — e.g. the demo's — which therefore never auto-confirm; the deprecated manual
+  confirm covers them). `HostEscrow.ResticPwSHA256` + `SaveHostEscrow` gains the param (last-write-wins);
+  NULL-safe reads via COALESCE. New `GetEscrowStatusForCustomer` (hosts⋈host_escrow; latest-updated wins).
+- `internal/api`: `escrowUploadRequest.restic_pw_sha256,omitempty` (the agent emit struct's mirror —
+  `TestEscrowUploadContract` updated in lockstep with the agent's half); stored on upload. The **report ACK**
+  gains `escrow: {identity_blob_present, restic_pw_sha256, created_at}` — omitted entirely when the customer
+  has no escrow row (a fresh customer stays pending silently).
+- Tests: hash stored + legacy-upload reads back NULL-safe as ""; ACK carries the object / omits it without a
+  row; contract mirror.
+
 ## v0.39.0 — offsite hardening: F4 credential re-issue + F2 scan retry + F5 save UX (2026-07-09)
 
 Part of the offsite-provisioning hardening bundle (pairs with controller v0.107.0 + agent v0.78.0); the