docs: R-191 closed, R-190 mitigation shipped (mechanism open), R-194 filed

R-191: the gate was run first and it mattered — ep0's prune jobs have run daily
since 2026-07-27 (18 tasks, all OK). THREE of my own queries said the opposite and
all three were broken instruments (worker-type vs worker_type, prune vs prunejob,
proxmox-backup vs proxmox-backup-proxy); acting on any would have disabled the only
pruning attempt while reporting that nothing prunes.

R-190: the row now reflects the MITIGATION, not the cause, and says so. Includes
that v0.124.0's transition record failed in production while every unit test
passed, and Part 3's single pass — the token-rotation class is real and documented
in our own installer but does not fit this box (same token still authenticates, the
other three grants survived, no installer run evidenced); ruled out on this box, not
fleet-wide.

R-194: PVE caches permissions (~40s and ~16min measured), so a single permission
read is a lagging indicator and may explain when R-190's refusal surfaced.

07-backup-architecture: the offsite retention row was RIGHT and the configuration
disagreed with it — noted, since a doc that states a contract does not enforce it.

documentation/architecture/07-backup-architecture.md

@@ -278,7 +278,10 @@ The tiers are **inputs to recovery**, not recovery routes. §7 and §8 say what
 | **Tier-2** cross-drive | `<target nsRoot>/backups/secondary/<app>/` | **always** a full mirror of the unit (`tier2.go:368-369`) **plus** `mandatory + optional` file legs, v2 layout `hdd/<rel>` + `userdata/<rel>` | nightly at W+60m | mirror (rsync) | no |
 | **Tier-3** restic offsite | Hetzner Storage Box over SFTP, one multi-path snapshot per app per run | the unit **plus** `mandatory` legs only; a separate `_shares` snapshot | nightly at W+105m | `--keep-daily 7 --keep-weekly 4 --keep-monthly 6` | **yes** (restic) |
 | **Plane-2** whole-guest, local | `local:` → `/var/lib/vz/dump` on the host | rootfs + `mp0 /var/lib/docker` + `mp1 /mnt/sys_drive` | **24 h** (`backup_cadence_seconds: 0`) | `local_backup_retention: 3` | **no** |
-| **Plane-2** whole-guest, offsite | `felhom-pbs:` → ep0 datastore `felhom-offsite`, per-customer namespace, over WireGuard | same contents | **7 days** (`604800`) | server-side prune on ep0, `keep-last 2` at `03:30` | **yes** (per-customer key) |
+| **Plane-2** whole-guest, offsite | `felhom-pbs:` → ep0 datastore `felhom-offsite`, per-customer namespace, over WireGuard | same contents | **7 days** (`604800`) | server-side prune on ep0, `keep-last 2` at `03:30` — **and the box asks for none** (R-191) | **yes** (per-customer key) |
+
+> **R-191 (2026-08-04) — this row was RIGHT and the configuration disagreed with it, weekly, for as long as R-89 has been in force.** The contract has not changed: offsite retention is ep0's, the box's token is write-only, and the box cannot delete its own history. What had not followed was the installer's `keep_last: 2` on the offsite tier, so every weekly run uploaded its snapshot successfully and then failed the whole JOB on a prune the token is refused — `whole_guest_backup_failed` in the operator's inbox about a backup that had already succeeded. Fixed in installer **1.25.0** (`keep_last: 0`) and on both live boxes; a gate now asserts it. **Verified before changing it:** ep0's two prune jobs have run every day since 2026-07-27, 18 tasks, all OK. A doc that states the contract does not enforce it — the gate does.
+
 
 **[FACT]** The three nightly legs derive from **one** customer-settable window start W at fixed
 offsets — db-dump at W, Tier-2 at W+60m, offsite at W+105m — so they can never be misordered