Merge master (#1706 participants-picker ordering) into card/1710

deletionFlash() (added by #1567) pluralised the count, the noun, the
auxiliary and the pronoun, but left the verb fixed at "stay" — so the
singular branch, which is the common one, shipped "1 ticket was merged
into it ... so it stay usable".

The verb agrees with the pronoun, so it belongs in the same ternary:
"it stays" / "they stay". Nothing else about the message changes.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/Http/Controllers/TicketController.php

@@ -776,12 +776,14 @@ class TicketController extends Controller
 
         if ($handled['unmerged'] !== []) {
             $parts[] = sprintf(
-                '%s %s merged into it and %s been un-merged (status %s) so %s stay usable: %s.',
+                '%s %s merged into it and %s been un-merged (status %s) so %s usable: %s.',
                 count($handled['unmerged']),
                 count($handled['unmerged']) === 1 ? 'ticket was' : 'tickets were',
                 count($handled['unmerged']) === 1 ? 'has' : 'have',
                 Ticket::STATUS_UNMERGED,
-                count($handled['unmerged']) === 1 ? 'it' : 'they',
+                // The verb agrees with the pronoun, so it lives in the same ternary:
+                // "so it stays usable" / "so they stay usable".
+                count($handled['unmerged']) === 1 ? 'it stays' : 'they stay',
                 implode(', ', $handled['unmerged']),
             );
         }