v0.133.0: a restore-test can never fill a box's disk; leftovers retried on a timer (R-672, R-673)

Space preflight before anything is created (uncompressed size from the vzdump log / PBS
snapshot, x1.2 + 5 GiB, thin metadata, off the tested guest's pool when another storage
is eligible, unknown refuses, reported as a non-pass result). Failed scratch teardown and
the stale-lock sweep retried every 10 min (the sweep under the heavy-op gate). A thin
pool crossing 90% requests an immediate host report. Six red-proofs.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

internal/backup/schedule.go

@@ -208,9 +208,11 @@ func (s *Scheduler) tick(ctx context.Context) {
 	spec := s.spec(ctx, archive)
 	spec.Archive = archive
 	res := s.runner.RunRestoreTest(ctx, spec)
-	if res.Skipped {
+	if res.Skipped && res.SkipReason == "" {
 		return // already logged by the engine (no free scratch VMID)
 	}
+	// R-672: a SPACE refusal is the test's result — reported (pass=false, the reason as the error),
+	// never dropped and never a pass. It earns no rotation credit, so the tier stays due.
 	rt := ToHubRestoreTest(res, s.now())
 	s.store.RecordRestoreTest(rt)
 	// Rotation credit is given ONLY on success. A failing tier must keep sorting first, or a tier