feat(helpdesk): ticket detail drawer — third drawer consumer

Migrates the ticket detail view (communication feed + ticket metadata aside)
into the core detail drawer pattern. Click a ticket number in the customer's
support tab → drawer slides in with the full ticket thread; arrow icons step
through the current filter page; ↗ opens the full page.

- `modules/helpdesk/templates/helpdesk-ticket-detail.phtml` extracts the
  body (communication feed container + metadata aside + i18n JSON) so the
  full page and the fragment render from the same source.
- `ticket-fragment($id).php` / `(none).phtml` reuse BcODataGateway::getTicket
  and enforce the same ABILITY_ACCESS guard as the full page. Connection
  errors render inline without aborting the fragment.
- Route `helpdesk/ticket-fragment/{id}` declared in module.php.
- `helpdesk-detail.js` wires the tickets grid: ticket-no formatter emits
  `data-drawer-trigger`, `linkColumn` disabled, `initDetailDrawer` called
  with `onContentLoaded → initHelpdeskTicket(contentEl)` so the async
  communication feed loads inside the drawer just like on the full page.
- `fetchUrl`/`fullUrl` written as single-expression arrows so the
  DetailDrawerFragmentContractTest can discover the consumer and validate
  the fragment endpoint files exist — the test now covers all three drawer
  consumers (address book, admin users, helpdesk tickets).

The full-page ticket view is unchanged for users who deep-link directly;
only the router-to-body wiring moved through the partial.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

modules/helpdesk/module.php

@@ -23,6 +23,7 @@ return [
         ['path' => 'helpdesk/domain-detail-data', 'target' => 'helpdesk/domain-detail-data'],
         ['path' => 'helpdesk/debitor/{id}', 'target' => 'helpdesk/debitor'],
         ['path' => 'helpdesk/ticket/{id}', 'target' => 'helpdesk/ticket'],
+        ['path' => 'helpdesk/ticket-fragment/{id}', 'target' => 'helpdesk/ticket-fragment'],
         ['path' => 'helpdesk/settings', 'target' => 'helpdesk/settings'],
         ['path' => 'helpdesk/settings/test-connection-data', 'target' => 'helpdesk/settings/test-connection-data'],
         ['path' => 'helpdesk/settings/diagnose-data', 'target' => 'helpdesk/settings/diagnose-data'],