fix(scheduling): harden edit/reschedule after review

Address findings from 3 review agents on the edit/reschedule feature:

- Race (correctness): handleEdit now marks the old message as cancelling
  while its cancel is in flight, so its Edit/Cancel buttons are disabled.
  Previously the old row stayed live during the fire-and-forget cancel, so
  a fast second edit could orphan a still-scheduled event and send twice.

- Durability (correctness): on a failed cancel-old, re-insert the old
  message if auto-prune removed its row while the modal was open, so the
  still-live delayed event stays visible and retriable instead of failing
  silently. Also clear any stale cancel error when starting an edit.

- a11y: per-row Edit/Cancel buttons now carry distinct aria-labels that
  include the message preview and send-time, so screen-reader users can
  tell which of several scheduled messages each button targets.

- UX: modal gains a submitLabel prop; the edit flow shows "Reschedule"
  instead of "Schedule". Modal now focuses the message body on open.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/room/ScheduleMessageModal.tsx

@@ -30,6 +30,8 @@ interface ScheduleMessageModalProps {
   initialSendAt?: number;
   /** Header title; defaults to "Schedule Message". */
   title?: string;
+  /** Primary-button label; defaults to "Schedule" (e.g. "Reschedule" when editing). */
+  submitLabel?: string;
   onScheduled: (delayId: string, sendAt: number, content: IContent) => void;
   onClose: () => void;
 }
@@ -94,6 +96,7 @@ export function ScheduleMessageModal({
   initialBody,
   initialSendAt,
   title = 'Schedule Message',
+  submitLabel = 'Schedule',
   onScheduled,
   onClose,
 }: ScheduleMessageModalProps) {
@@ -179,7 +182,7 @@ export function ScheduleMessageModal({
       <OverlayCenter>
         <FocusTrap
           focusTrapOptions={{
-            initialFocus: false,
+            initialFocus: '#schedule-message-body',
             onDeactivate: onClose,
             clickOutsideDeactivates: true,
             escapeDeactivates: stopPropagation,
@@ -341,7 +344,7 @@ export function ScheduleMessageModal({
                 disabled={submitting || !preview}
                 before={submitting ? <Spinner variant="Primary" size="100" /> : undefined}
               >
-                <Text size="B400">Schedule</Text>
+                <Text size="B400">{submitLabel}</Text>
               </Button>
             </Box>
           </Dialog>

src/app/features/room/ScheduledMessagesTray.tsx

@@ -115,12 +115,25 @@ export function ScheduledMessagesTray({ roomId }: ScheduledMessagesTrayProps) {
   // cancel leaves it visible (and retriable) instead of letting it silently fire.
   const handleEdit = useCallback(
     (oldMsg: ScheduledMessage, newDelayId: string, sendAt: number, content: IContent) => {
+      // Add the newly-scheduled message up front (nothing lost yet).
       setScheduledMessages((prev) => {
         const next = new Map(prev);
         const current = (next.get(roomId) ?? []).filter((m) => m.delayId !== newDelayId);
         next.set(roomId, [{ delayId: newDelayId, roomId, content, sendAt }, ...current]);
         return next;
       });
+      // Mark the old message as cancelling so its row's Edit/Cancel buttons are
+      // disabled while we tear it down. Without this the old row stays live during
+      // the in-flight cancel and a second edit could orphan a still-scheduled event
+      // (both would fire). Also clear any stale error from a prior failed cancel.
+      setCancelling((prev) => new Set(prev).add(oldMsg.delayId));
+      setCancelErrors((prev) => {
+        if (!prev.has(oldMsg.delayId)) return prev;
+        const next = new Set(prev);
+        next.delete(oldMsg.delayId);
+        return next;
+      });
+      setEditing(null);
       cancelScheduledMessage(mx, oldMsg.delayId)
         .then(() => {
           setScheduledMessages((prev) => {
@@ -131,8 +144,28 @@ export function ScheduledMessagesTray({ roomId }: ScheduledMessagesTrayProps) {
             return next;
           });
         })
-        .catch(() => setCancelErrors((prev) => new Set(prev).add(oldMsg.delayId)));
+        .catch(() => {
-      setEditing(null);
+          // Cancel failed — the old delayed event is still live server-side, so it
+          // must stay visible and retriable. Re-insert it if auto-prune removed the
+          // row while the modal was open, otherwise the failure (and the duplicate
+          // it will send) would be invisible.
+          setScheduledMessages((prev) => {
+            const next = new Map(prev);
+            const current = next.get(roomId) ?? [];
+            if (!current.some((m) => m.delayId === oldMsg.delayId)) {
+              next.set(roomId, [...current, oldMsg]);
+            }
+            return next;
+          });
+          setCancelErrors((prev) => new Set(prev).add(oldMsg.delayId));
+        })
+        .finally(() => {
+          setCancelling((prev) => {
+            const next = new Set(prev);
+            next.delete(oldMsg.delayId);
+            return next;
+          });
+        });
     },
     [mx, roomId, setScheduledMessages],
   );
@@ -147,6 +180,7 @@ export function ScheduledMessagesTray({ roomId }: ScheduledMessagesTrayProps) {
           initialBody={typeof editing.content.body === 'string' ? editing.content.body : ''}
           initialSendAt={editing.sendAt}
           title="Edit scheduled message"
+          submitLabel="Reschedule"
           onScheduled={(newDelayId, sendAt, content) =>
             handleEdit(editing, newDelayId, sendAt, content)
           }
@@ -183,7 +217,11 @@ export function ScheduledMessagesTray({ roomId }: ScheduledMessagesTrayProps) {
       {/* Tray items */}
       {expanded && (
         <Box direction="Column">
-          {messages.map((msg) => (
+          {messages.map((msg) => {
+            const bodyPreview =
+              typeof msg.content.body === 'string' ? (msg.content.body as string) : '(message)';
+            const rowDesc = `${bodyPreview} at ${formatSendAt(msg.sendAt)}`;
+            return (
             <Box
               key={msg.delayId}
               direction="Column"
@@ -203,9 +241,7 @@ export function ScheduledMessagesTray({ roomId }: ScheduledMessagesTrayProps) {
                     whiteSpace: 'nowrap',
                   }}
                 >
-                  {typeof msg.content.body === 'string'
+                  {bodyPreview}
-                    ? (msg.content.body as string)
-                    : '(message)'}
                 </Text>
                 <Text size="T200" priority="300" style={{ whiteSpace: 'nowrap', flexShrink: 0 }}>
                   {formatSendAt(msg.sendAt)}
@@ -214,7 +250,7 @@ export function ScheduledMessagesTray({ roomId }: ScheduledMessagesTrayProps) {
                   size="300"
                   radii="300"
                   variant="SurfaceVariant"
-                  aria-label="Edit scheduled message"
+                  aria-label={`Edit scheduled message: ${rowDesc}`}
                   disabled={cancelling.has(msg.delayId)}
                   onClick={(e) => {
                     e.stopPropagation();
@@ -227,7 +263,7 @@ export function ScheduledMessagesTray({ roomId }: ScheduledMessagesTrayProps) {
                   size="300"
                   radii="300"
                   variant="SurfaceVariant"
-                  aria-label="Cancel scheduled message"
+                  aria-label={`Cancel scheduled message: ${rowDesc}`}
                   disabled={cancelling.has(msg.delayId)}
                   onClick={(e) => {
                     e.stopPropagation();
@@ -246,7 +282,8 @@ export function ScheduledMessagesTray({ roomId }: ScheduledMessagesTrayProps) {
                 </Text>
               )}
             </Box>
-          ))}
+            );
+          })}
         </Box>
       )}
       </Box>