pick-up sets the ticket to in_progress on accept (T-339)

When a ticket is handed to a live Claude pane (T-327), advance it to
in_progress on the receiving side of the bus — gated on acceptance, so a
pick-up with no live session stays a quiet no-op and never mutates state.
Only a not-yet-started ticket (backlog/ready) transitions, so re-picking
up a review/done ticket doesn't drag it backwards. On success it publishes
(builtin.tickets, changed) so the sidebar refreshes.

The handler logic moves into a testable applyTicketPickUp() seam; the
sidebar button now carries the current status in the pick-up payload.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/builtin/tickets/src/tickets_view.dart

@@ -328,7 +328,9 @@ class _PickUpAction extends StatelessWidget {
         unawaited(() async {
           final resp = await kernel.ipc.request('pql.tickets.show', args: {'id': id, 'withContext': true});
           if (!resp.ok) return; // a missing ticket / failed fetch is a quiet no-op
-          kernel.messages.publish('builtin.tickets', 'pick-up', {'id': id, 'prompt': pickUpPrompt(resp.data)});
+          // Carry the current status so the receiver can gate the in_progress
+          // transition without a second fetch (T-339).
+          kernel.messages.publish('builtin.tickets', 'pick-up', {'id': id, 'prompt': pickUpPrompt(resp.data), 'status': resp.data['status']});
         }());
       },
       builder: (ctx, hovered, _) => Padding(