v0.175.0 — R-82: a tier that overruns the quiesce bound defers the rest

Operator ruling 2026-07-26: let the first backup run as long as needed; other
backups shouldn't start until finished.

A first FULL offsite snapshot runs for hours, far past max_quiesce. When that
bound elapses the app resumes (unchanged), but the loop then started the NEXT
tier while the first was still uploading. Now it breaks and defers the rest to
a later poll — vzdump still holds the guest lock, so the second start would be
refused by the agent (409, v0.99.0) or fail on the lock, and a failed backup
never satisfies a cadence, so the tier would retry into the same wall forever.

pollTier returns (phase, stillRunning, err). The app still resumes exactly once.

Red-proof observed and restored; full suite green.

CHANGELOG.md

@@ -1,5 +1,28 @@
 ## Changelog
 
+### v0.175.0 — R-82: a tier that overruns the quiesce bound defers the rest (2026-07-26)
+
+Operator ruling 2026-07-26: *"let the first backup run as long as needed; other backups shouldn't
+start until finished."*
+
+A first FULL offsite snapshot legitimately runs for **hours** — far past `max_quiesce`. When that
+bound elapses the app resumes (correct, and unchanged), but `quiesceAndPollTiers` then moved on and
+started the NEXT tier while the first was still uploading. That is now a `break`: the remaining tiers
+are deferred to a later poll.
+
+Why it matters: vzdump still holds the guest lock, so the second start would be **refused by the
+agent (409, v0.99.0)** or fail on the lock — and a failed backup never satisfies a cadence, so the
+tier would stay permanently due and retry into the same wall every poll.
+
+`pollTier` now returns `(phase, stillRunning, err)`; `stillRunning` means the bound elapsed with the
+backup still going. Nothing else changed — the app still resumes exactly once, on the same guard.
+
+**Tests:** `TestTierOverrunsQuiesceBound_RemainingTiersDeferred`. Red-proof observed: dropping the
+`break` starts the second tier and the test fails with
+`the second tier MUST NOT start while the first is still running; started=[local felhom-pbs]`.
+Restored; full suite green.
+
+
 ### v0.174.0 — R-82 Slice B: one quiesce window, two backup tiers (2026-07-26)
 
 **MinAgent UNCHANGED — deliberately.** This release degrades gracefully against ANY older agent; it