chore(search-sync-worker): address CodeRabbit nits on collection + drain helper

- spotlight.go / user_room.go: move the HistorySharedSince short-circuit
  ahead of the Accounts validation. Previously a restricted-room event
  with an empty Accounts slice returned an "empty accounts" error
  instead of being silently skipped like every other restricted event.
  Matches the event-level contract documented on InboxMemberEvent.
- inbox_integration_test.go: surface batch.Error() after draining each
  fetch so mid-batch server errors (consumer deleted, leader change)
  fail the test with their real cause instead of a misleading
  "drained N of M" mismatch.

https://claude.ai/code/session_01XTmSpmv5dT6UXX7NpRdYqN

Author: claude

search-sync-worker/inbox_integration_test.go

@@ -110,6 +110,10 @@ func drainConsumer(
 			handler.Add(msg)
 			received++
 		}
+		// Surface any mid-batch error (consumer deleted, leader change,
+		// transient connection). Without this, batch.Messages() just closes
+		// silently and only the outer Equal would fail — losing the root cause.
+		require.NoError(t, batch.Error(), "batch error after draining (attempt %d, received %d of %d)", attempts, received, expected)
 	}
 	require.Equal(t, expected, received, "drained %d of %d expected messages", received, expected)
 	handler.Flush(ctx)

search-sync-worker/spotlight.go

@@ -55,12 +55,16 @@ func (c *spotlightCollection) BuildAction(data []byte) ([]searchengine.BulkActio
 	if payload.RoomID == "" {
 		return nil, fmt.Errorf("build spotlight action: missing roomId")
 	}
-	if len(payload.Accounts) == 0 {
-		return nil, fmt.Errorf("build spotlight action: empty accounts")
-	}
+	// Event-level restricted-room short-circuit runs BEFORE account
+	// validation so restricted events with any payload shape (including an
+	// empty Accounts slice) are uniformly skipped per the InboxMemberEvent
+	// contract — no surprise error on an otherwise-valid "skip me" event.
 	if payload.HistorySharedSince != 0 {
 		return nil, nil
 	}
+	if len(payload.Accounts) == 0 {
+		return nil, fmt.Errorf("build spotlight action: empty accounts")
+	}
 
 	actions := make([]searchengine.BulkAction, 0, len(payload.Accounts))
 	for i, account := range payload.Accounts {

search-sync-worker/user_room.go

@@ -87,12 +87,16 @@ func (c *userRoomCollection) BuildAction(data []byte) ([]searchengine.BulkAction
 	if payload.RoomID == "" {
 		return nil, fmt.Errorf("build user-room action: missing roomId")
 	}
-	if len(payload.Accounts) == 0 {
-		return nil, fmt.Errorf("build user-room action: empty accounts")
-	}
+	// Event-level restricted-room short-circuit runs BEFORE account
+	// validation so restricted events with any payload shape (including an
+	// empty Accounts slice) are uniformly skipped per the InboxMemberEvent
+	// contract — no surprise error on an otherwise-valid "skip me" event.
 	if payload.HistorySharedSince != 0 {
 		return nil, nil
 	}
+	if len(payload.Accounts) == 0 {
+		return nil, fmt.Errorf("build user-room action: empty accounts")
+	}
 
 	ts := evt.Timestamp
 	roomID := payload.RoomID