R-403: a poorer copy must never delete a richer one

MEASURED FIRST, then fixed. On the shipped v0.229.0, on demo-hp, an app's Tier-2 copy went from
120 082 104 B (4 database dumps + 3 named-volume tars) to 7 036 B (none of either) in ONE nightly
run, and the run recorded itself a success: 'Tier 2 copied docmost -> ... (14.9 KB, 0 leg(s), 0s)'.
Evidence: felhom.eu/documentation/audits/DRILL-r403-tier2-delete-2026-08-31/.

The mechanism was three individually-correct lines: RunTier2 guards the unit leg with os.Stat only
(does the folder exist), rsyncMirror is rsync -a --delete, and nothing between them compared source
to destination. An EMPTY unit is a folder that exists.

THE GUARD. One predicate, unitCarriesData/unitIsHollow (r403_hollow.go), asking the MANIFEST and
never the byte size - a big compose tree with no dumps is dangerous, a tiny unit for a tiny app is
fine. Fail closed on an absent or unparseable manifest. RunTier2 skips the unit leg when the source
is hollow AND the destination is not; the other legs still run, the run is not failed, and the skip
is recorded for the SURFACE (CrossDriveBackup.UnitLegSkipped + UnitPackageDate) as well as logged.

--delete STAYS and shrinking stays legal. 07 section 8 row 5's derived-copy rule is unchanged; the
fence is exactly one shape. TestR403_DataLegShrinkIsUnaffected is the guard on the guard.

THE HONESTY. A preserved package is older than the run that preserved it, so the card carries a
notice and the unit-restore confirm names the PACKAGE's date - read from the mirrored manifest's own
created_at, not from the status record - plus a clause saying why it is older.

THE CAUSE. RestoreTier2Unit now refills a hollow or absent primary unit from the mirror it just
restored from, INSIDE the call before returning. The hollow manifest was written two seconds after
a restore by the 5-minute capture job; any follow-up job races it. The capture itself is NOT guarded:
a capture describing an empty drive as empty is correct, and with the primary refilled there is no
hollow state left to describe. Never over a complete primary, never after a failed restore.

recordTier2Success and tier2UnitConfirmMsg keep their old signatures as thin callers, so no existing
test needed editing. New seam unitRehydrate, separate from tier2Mirror on purpose.

22 new Go tests. Red-proofs run and reverted: A6 (predicate -> size threshold), B1 (guard removed ->
the copy's 3 files are DELETED and the seam is called), B6 (a general never-shrink rule -> the shrink
case fails), C2 (only-when-hollow dropped -> the complete primary is overwritten).

controller/internal/web/handlers.go

@@ -1203,6 +1203,9 @@ type AppBackupRow struct {
 	// Tier2UnitConfirm is the assembled destructive-confirm sentence (tier2UnitConfirmMsg). Built in
 	// Go, not in the attribute, so it is one named string a test can assert verbatim.
 	Tier2UnitConfirm string
+	// Tier2UnitStaleNotice (R-403) — non-empty when the newest run PRESERVED this copy's package
+	// instead of refreshing it, so the card cannot render a preserved package as a fresh one.
+	Tier2UnitStaleNotice string
 
 	// Drive disconnected — app's home drive is currently disconnected
 	DriveDisconnected bool
@@ -1428,8 +1431,14 @@ func (s *Server) buildAppBackupRows(status *backup.FullBackupStatus) []AppBackup
 				// row keeps rendering everything else it already showed.
 				if cov, covErr := s.backupMgr.Tier2RestoreCoverage(app.StackName); covErr == nil {
 					row.Tier2UnitRestorable = cov.CanRestoreUnit()
-					row.Tier2CopyDate, row.Tier2CopyDateProven = cov.Tier2CopyDate()
-					row.Tier2UnitConfirm = tier2UnitConfirmMsg(row.Tier2CopyDate, row.Tier2CopyDateProven)
+					// R-403: the UNIT action names the PACKAGE's date, not the run's. After a
+					// preserved leg those are different dates and the run's is the flattering one.
+					pkgDate, stale := cov.UnitRestoreDate()
+					row.Tier2CopyDate, row.Tier2CopyDateProven = pkgDate, cov.CopyLastSuccess != ""
+					row.Tier2UnitConfirm = tier2UnitConfirmWithStaleness(pkgDate, row.Tier2CopyDateProven, stale)
+					if stale && pkgDate != "" {
+						row.Tier2UnitStaleNotice = fmt.Sprintf(tier2UnitStaleNoticeFmt, fmtRFC3339Local(pkgDate))
+					}
 				}
 				switch cd.LastStatus {
 				case "ok":
@@ -1669,6 +1678,16 @@ const (
 	tier2UnitConfirmDateUnprovenFmt = " A másolat kelte: %s – ez az utolsó mentési kísérlet ideje, azt nem tudjuk igazolni, hogy sikeres volt."
 
 	tier2UnitConfirmContrast = " A mellette lévő „Fájlok visszaállítása” ezzel szemben csak a hiányzó fájlokat pótolja, és semmit nem ír felül. Az alkalmazás a művelet idejére leáll."
+
+	// tier2UnitStaleClause (R-403) — the package in this copy is OLDER than the copy's newest run,
+	// because that run PRESERVED it rather than replacing it with an empty one. Without this the
+	// confirm would name a date the customer reads as "last night" over a package from before it.
+	// The whole point of preserving the copy is lost if the surface then misdescribes what it kept.
+	tier2UnitStaleClause = " FIGYELEM: ennek a másolatnak az adatcsomagja régebbi, mint a legutóbbi mentés — a fő meghajtón lévő csomag hiányos volt, ezért a meglévő, teljes másolatot megőriztük. A visszaállítás a fent megadott csomagot használja."
+
+	// tier2UnitStaleNoticeFmt (R-403) — the same fact on the per-app backup card, where the customer
+	// looks BEFORE deciding anything. %s is the package's own date.
+	tier2UnitStaleNoticeFmt = "A másolat adatcsomagja régebbi, mint a legutóbbi mentés (%s): a fő meghajtón lévő csomag hiányos volt, ezért a meglévő, teljes másolatot megőriztük."
 )
 
 // tier2UnitConfirmMsg assembles the destructive confirm for one app's Tier-2 unit restore. Pure, so
@@ -1677,6 +1696,13 @@ const (
 // A copy with no recorded date at all still gets a confirm — it just cannot name one. Dropping the
 // whole confirm because a date is missing would remove the warning and keep the destruction.
 func tier2UnitConfirmMsg(copyDate string, proven bool) string {
+	return tier2UnitConfirmWithStaleness(copyDate, proven, false)
+}
+
+// tier2UnitConfirmWithStaleness is tier2UnitConfirmMsg for a copy whose PACKAGE may be older than its
+// newest run (R-403). ONE implementation, two callers — the two-argument form above is the ordinary
+// case where the run really did refresh the package.
+func tier2UnitConfirmWithStaleness(copyDate string, proven bool, stale bool) string {
 	msg := tier2UnitConfirmBase
 	if copyDate != "" {
 		if proven {
@@ -1685,7 +1711,12 @@ func tier2UnitConfirmMsg(copyDate string, proven bool) string {
 			msg += fmt.Sprintf(tier2UnitConfirmDateUnprovenFmt, fmtRFC3339Local(copyDate))
 		}
 	}
-	return msg + tier2UnitConfirmContrast
+	msg += tier2UnitConfirmContrast
+	// R-403 last, so it is the sentence the customer is left holding before they press.
+	if stale {
+		msg += tier2UnitStaleClause
+	}
+	return msg
 }
 
 // tier2UnitSourceMsg renders the "which copy" clause for the Tier-2 unit restore's outcome, or "" if