installer 1.25.0: the off-site tier stops asking to prune (R-191)

Every weekly off-site run uploaded successfully and then failed the job on a prune
the box's token is deliberately refused — R-89 moved off-site pruning server-side
to ep0 and box tokens stay write-only. The 2026-07-26 'two weeks' ruling was not
reversed; where it is enforced moved, and keep_last: 2 did not follow. Now 0,
which the agent's existing guard already reads as 'never prune from the box'.

Verified read-only on ep0 before changing it: both namespaces have a prune job at
03:30 keep-last 2 that has run every day since 2026-07-27 — 18 tasks, all OK, the
newest keeping exactly two. Without that check this would have traded a weekly
false alarm for unbounded growth.

A gate asserts the offsite tier carries no client-side prune. The local tier is
untouched.

scripts/felhom-host-install.sh

@@ -184,7 +184,7 @@
 
 set -euo pipefail
 
-SCRIPT_VERSION="1.24.0"   # the SINGLE version source (F-1): -h and the run banners follow it.
+SCRIPT_VERSION="1.25.0"   # the SINGLE version source (F-1): -h and the run banners follow it.
                           # The hub used to carry a copy for its Setup tab; R-94 DELETED it
                           # (2026-08-02) because the hub cannot know which version a box runs —
                           # the Setup command fetches this script at run time. scripts/
@@ -2479,8 +2479,30 @@ for _k,_v in {"unit_dir":"/etc/systemd/system","stage_dir":"/var/lib/felhom-agen
 base.setdefault('storage', {"watchdog_interval_seconds":5,"watchdog_debounce_seconds":15,"known_refresh_seconds":20})
 # R-82: local DAILY + offsite WEEKLY. The two tiers carry SEPARATE cadences and retentions —
 # keep_last=3 is three DAYS on the daily tier and three WEEKS on a weekly one, so one shared knob
-# would guarantee that one of them is wrong. keep_last=2 on the offsite tier = two weeks (operator
-# ruling 2026-07-26).
+# would guarantee that one of them is wrong.
+#
+# THE OFFSITE TIER CARRIES NO CLIENT-SIDE RETENTION, AND THAT IS THE POINT (R-191, 2026-08-04).
+# It used to be written `keep_last: 2` ("two weeks", operator ruling 2026-07-26). **R-89 then moved
+# offsite pruning SERVER-SIDE** — ep0 runs a per-namespace prune job and box tokens stay write-only,
+# deliberately, so that a box can never delete its own offsite history. The 2026-07-26 ruling was not
+# reversed; where it is ENFORCED moved, and this value did not follow.
+#
+# The consequence was weekly and wrong in the worst direction: vzdump UPLOADED the snapshot fine and
+# then failed the whole job on the prune the token is refused —
+#   `prune 'ct/9201': permission check failed - missing Datastore.Modify|Datastore.Prune`
+# → `TASK ERROR: job errors` → `whole_guest_backup_failed` in the operator's inbox. Every week, on
+# both boxes, about a backup that had already succeeded. A tier that cries wolf weekly is a tier
+# whose real failure nobody will see.
+#
+# VERIFIED BEFORE CHANGING IT (2026-08-04, read-only on ep0): prune jobs `prune-demo-felhom` and
+# `prune-demo-hp` exist on datastore `felhom-offsite`, one per namespace, schedule 03:30, keep-last 2,
+# and have run EVERY DAY since 2026-07-27 — 18 tasks, all `status=OK`, the newest showing
+# `retention options: --ns demo-felhom --max-depth 0 --keep-last 2` and keeping exactly two. Retention
+# happens; it happens THERE. **If that ever stops being true, this zero is unbounded growth** — check
+# ep0's prune jobs before assuming the offsite tier is retained.
+#
+# `keep_last: 0` means "never prune from the box" and is the value the agent's own guard reads
+# (allowPBSPrune = !primary && keep_last > 0), so no agent change is needed to honour it.
 #
 # The offsite tier is written even though `felhom-pbs` does not exist yet: that storage appears only
 # when the hub provisions the DR tier. The agent DEFERS a tier whose target storage is absent
@@ -2491,7 +2513,7 @@ base.setdefault('storage', {"watchdog_interval_seconds":5,"watchdog_debounce_sec
 # setdefault: an EXISTING box's backup block is preserved WHOLE. Upgrades never gain the tier here —
 # they are migrated explicitly (R-82 Slice D.2), so an in-place upgrade can never silently start
 # writing to an offsite datastore.
-base.setdefault('backup', {"local_backup_target":os.environ.get('BACKUP_TARGET_RESOLVED','local'),"local_backup_retention":3,"restore_storage":"local-lvm","restore_test_cadence_seconds":0,"scratch_vmid_min":990000,"scratch_vmid_max":990009,"pbs_secret_dir":"/etc/pve/priv/storage","backup_cadence_seconds":0,"backup_targets":[{"target_id":"felhom-pbs","cadence_seconds":604800,"keep_last":2}]})
+base.setdefault('backup', {"local_backup_target":os.environ.get('BACKUP_TARGET_RESOLVED','local'),"local_backup_retention":3,"restore_storage":"local-lvm","restore_test_cadence_seconds":0,"scratch_vmid_min":990000,"scratch_vmid_max":990009,"pbs_secret_dir":"/etc/pve/priv/storage","backup_cadence_seconds":0,"backup_targets":[{"target_id":"felhom-pbs","cadence_seconds":604800,"keep_last":0}]})
 base.setdefault('local_api', {})
 base['local_api'].setdefault('enable', True)
 base['local_api']['listen_addr'] = os.environ['BRIDGE_ADDR']