hub v0.89.0 — the two halves of decision D-c (R-167, R-158)

New OPERATOR-ONLY event type recovery_unit_capture_failed (controller
v0.191.0, R-158): in allowedEventTypes AND notify.operatorOnlyEvents.
Deliberately not a reuse of backup_failed, which carries customer copy and
sits in the controller's DefaultEnabledEvents — reusing it would email the
customer in Hungarian about a failure they cannot act on. R-158's own
proposal said backup_failed; D-c overrides it.

disk_warning/disk_critical lose their generic customerMessages entries.
Both were allowlisted, copy'd, default-enabled and checkbox'd with NO
producer anywhere; controller v0.191.0 becomes that producer and sends a
DYNAMIC Hungarian message naming the drive and its free space.
FormatCustomerEmail prefers the entry over the message, so keeping a static
entry would discard the label and the byte figures — the same reason
offbox_enlarge_blocked and disk_health_degraded have none. The deletion is
pinned by a test.

New notify.IsOperatorOnly so the api package can pin BOTH registers of a new
event type in ONE test; allowlisted-but-not-operator-only is invisible when
they are checked separately, and it is the defect v0.78.0 shipped. The
register itself stays unexported.

REUSE.md's "new event type" extension point rewritten: it told readers to
always add a customerMessages entry, which is wrong for operator-only types
and harmful for dynamic-message ones.

Tests 574 -> 579. Red-proof: removing the operatorOnlyEvents entry shows the
customer being emailed; the skipped/operator_only row is asserted as a
positive observable.

hub/internal/api/handler.go

@@ -1573,6 +1573,20 @@ var allowedEventTypes = map[string]bool{
 	"whole_guest_backup_failed":    true,
 	"whole_guest_backup_recovered": true,
 
+	// R-158 / R-167 (controller v0.191.0, decision D-c): a per-app Tier-1 recovery-unit capture
+	// failed. Until then a `[WARN]` line in the controller reached no hub channel at all — the fifth
+	// instance in this project of a mechanism built and left disconnected.
+	//
+	// DELIBERATELY NOT `backup_failed`, for exactly the reason recorded above for the whole-guest
+	// pair: that type carries a customerMessages entry AND sits in the controller's
+	// DefaultEnabledEvents, so reusing it emails the CUSTOMER, in Hungarian, about a failure they
+	// cannot act on. R-158's original proposal named `backup_failed`; D-c routes this to the
+	// operator, and where the two disagree D-c wins.
+	//
+	// OPERATOR-ONLY IS ENFORCED BY `notify.operatorOnlyEvents` — see the paragraph above. This entry
+	// alone does NOT make it operator-only.
+	"recovery_unit_capture_failed": true,
+
 	// Controller-pushed events
 	"controller_started":      true,
 	"claim_lockout":           true, // v0.50.0 — claim/reset code brute-force lockout tripped