v0.283.0: apps go off-site by themselves (decision 50) with a size warning; a Stop holds during a backup (R-721); page slips (R-724/R-725)

Red-proofs RP31-RP38. MinAgent 0.131.0 (unchanged).

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

controller/internal/backup/offbox.go

@@ -1301,6 +1301,7 @@ func (m *Manager) runOffboxInternal(ctx context.Context, apps, base, env []strin
 	// Pre-run hygiene: clear any lock restic can prove stale before we start (cheap; the --remove-all
 	// crash-lock escalation lives in resticStep for the locks restic can't self-detect).
 	m.unlockStale(ctx, base, env)
+	m.RefreshOffsiteFit() // decision 50: the page's size estimate is taken before every push
 	var firstErr error
 	for _, stack := range apps {
 		src, ok := m.discoverOffboxUnit(stack)