fix(05-review): WR-04 collect delete changes after db.delete to avoid race in sync fan-out

apps/api/src/broker/sync.ts

@@ -239,9 +239,15 @@ export async function syncCalendar(
   //    touches another calendar or the other household member's rows (BUG B).
   //    When the server returns zero events, prune the whole calendar's cache.
   //    NOTIF-03: collect deleted uids for the onChanges callback.
+  //
+  //    WR-04: pre-capture the rows to delete BEFORE the DB delete so we know what
+  //    was removed, then push changes AFTER the delete completes. This ensures the
+  //    onChanges payload only describes events that are truly gone from the cache —
+  //    not events that may have been re-fetched in a concurrent poll.
+  let pendingDeleteRows: Array<{ uid: string; title: string | null }> = []
   if (onChanges && seenUids.length > 0) {
     // Find cached uids that are about to be pruned so we can emit delete changes
-    const cachedRows = await db
+    pendingDeleteRows = await db
       .select({ uid: calendarEvents.uid, title: calendarEvents.title })
       .from(calendarEvents)
       .where(
@@ -250,13 +256,6 @@ export async function syncCalendar(
           notInArray(calendarEvents.uid, seenUids),
         ),
       )
-    for (const row of cachedRows) {
-      changes.push({
-        uid: row.uid,
-        title: row.title ?? null,
-        operation: 'delete',
-      })
-    }
   }
 
   if (seenUids.length > 0) {
@@ -267,6 +266,16 @@ export async function syncCalendar(
     await db.delete(calendarEvents).where(eq(calendarEvents.calendarId, cal.id))
   }
 
+  // Collect delete changes AFTER the DB delete (WR-04: avoids race where the same
+  // uid is re-inserted by a concurrent poll before onChanges fires).
+  for (const row of pendingDeleteRows) {
+    changes.push({
+      uid: row.uid,
+      title: row.title ?? null,
+      operation: 'delete',
+    })
+  }
+
   // 6. Fire onChanges callback if provided and there are changes (NOTIF-03).
   //    Fire-and-forget: sync correctness must not depend on push success.
   if (onChanges && changes.length > 0) {