hub v0.93.0: the retention keeps the key it was built to keep (R-198) + three honesty fixes (R-197, R-192, R-196)

R-198 — host_escrow_superseded shipped with `blob` (the K-escrow / PBS datastore key) and
identity_blob was added to host_escrow LATER, never here. The offsite restic REPOSITORY
password lives in identity_blob. So demoteCurrentEscrowTx -- whose own comment calls it "THE
ONE escrow row-copy routine" -- retained the whole-guest key and silently dropped the off-site
data key, which is the secret the retention was built to preserve. And because the copy happens
as the new blob overwrites the old, the destroying act was the ESCROW CEREMONY: the exact thing
a rebuilt box tells its customer to run, on a card promising in Hungarian that the old backups
stay recoverable. Both demo boxes crossed that line on 2026-08-04.

  - identity_blob added to the table (CREATE + additive ALTER) and carried in the shared copy
    routine, so BOTH callers are fixed at once: re-escrow and host-delete demotion.
  - ListSupersededEscrow reads it back; store.HostEscrow gains IdentityBlob.
  - CountCurrentEscrowWithIdentity is the census of who the fix protects.
  - Nothing is backfillable: pre-v0.93.0 retained rows have no blob and their sources are gone.
  - Tests assert the CONSEQUENCE (a retained row can still yield a repo password), which is why
    the pre-existing retention test stayed green for two months asserting the mechanism.

R-197 — SaveHostEscrow returns the hash it replaced; the escrow PUT raises
offsite_repo_key_changed (warning, operator-only, edge-triggered) when both hashes are known and
differ. No hash value travels. Severity chosen for the world v0.93.0 creates: with the identity
blob retained, a changed key is "this history now depends on an older recovery code", not a loss.

R-192 (half) — the stuck alert now reports the two shapes it actually covers, burned and
regressed, each stating its own measurement; the regressed text withdraws the Re-issue
recommendation. Every self-heal refusal leaves a notification_log row with its reason. The
guard's logic is unchanged; its 500-oldest-reports scoping stays OPEN and the window is named in
the alert text so the limitation travels with the number. offsite_delivery_stuck and
offsite_credential_restaged are added to operatorOnlyEvents -- neither was registered and neither
has a customerMessages entry, which is not a block.

R-196 — five comments (not the three the spec expected) claimed ReissueCredentials rotates the
restic repo password. It resets the PROVIDER password and cannot touch the repo password, which
is generated on the box. All five corrected; the staleness mark documented as precautionary. The
BEHAVIOUR stays open.

Not in this release: R-199, R-200, R-201 remain open -- the chain that hands the key back is
still unassembled. Part 5 hit its gate; the orphan card is untouched (R-202).

documentation/architecture/03-host-agent.md

@@ -378,6 +378,42 @@ nicety.
   **loses Felhom's backup guarantees** — no PBS verify / monitoring on storage we can't reach. An
   honest signup-time tradeoff, not a hidden one.
 
+#### Custody across generations — what the hub retains when a blob is superseded (hub v0.60.0; **contract corrected hub v0.93.0, R-198**)
+
+A ceremony that seals a *different* passphrase does not destroy the blob it replaces: the hub copies
+the current `host_escrow` row into `host_escrow_superseded` **before** overwriting it, so a previous
+generation stays openable with the recovery code that sealed it. The same routine
+(`demoteCurrentEscrowTx`) is used when a host is deleted, which **demotes** custody rather than
+destroying it. The hub never decrypts either table.
+
+**The contract as originally shipped was incomplete, and the gap is worth recording because it was
+invisible for two months.** An escrow generation is **two** sealed artifacts — the K-escrow `blob`
+(the PBS datastore key `K`) and `identity_blob` (the age-wrapped `IdentityBundle`, which carries the
+offsite **restic repository password** as well as the tunnel/PBS tokens and the WG key). Retention
+covered only the first. So a supersession preserved the whole-guest key and destroyed the off-site
+data key — and because the copy happens as the new blob lands, **the destroying act was the ceremony
+itself**, i.e. the step a rebuilt box asks its customer to perform. Corrected in hub v0.93.0: the
+retained row carries both.
+
+**Two consequences that belong in this doc rather than a changelog:**
+
+- **Generational custody is now the recovery precondition for the offsite tier.** The operator ruled
+  on 2026-08-04 that no repository password is retained on the Proxmox host (R-193 candidate (c),
+  refused). With no host-side copy, a rebuilt box's only route back to its previous off-site history
+  is *the customer's older recovery code opening the retained identity blob* — which exists only if
+  the supersession that replaced it happened on hub v0.93.0 or later.
+- **Retention is custody, not recovery, and this doc must not be read as claiming otherwise.** The
+  hub's restore-mode serving of these blobs (§ slice 10D) has **no client** in the agent, the
+  controller's recovered-password injection seam has **no user interface**, and no part of the chain
+  has ever been exercised outside a unit test — the one live identity round-trip (2026-06-10)
+  predates the `ResticRepoPassword` field. Tracked as R-199/R-200/R-201; evidence
+  `documentation/audits/RECON-offsite-dr-chain-2026-08-04.md`.
+
+**The honesty property above is unchanged and now has a second edge:** losing `R` and the box makes
+the offsite backups unrecoverable by anyone — *and* an older generation's data is recoverable only
+with **that generation's** recovery code, which the customer must still hold. A current recovery code
+does not open a previous generation's blob.
+
 ## 9. Provisioning & DR flows
 
 **Provisioning (reconcile-driven, by restore).** Fresh creation of a Docker-capable LXC needs