docs: add UI/UX component guidelines and improve breadcrumb/tab-panel styling

Add "Komponenten in Formularen" section to boundaries-ui.md with rules
for core button classes, margin resets, checkbox sizing, sticky positioning,
icon-only buttons, responsive grids, and CSS variables. Add matching
quick-reference bullets to CLAUDE.md UI Patterns section.

Fix breadcrumb wrapping: nowrap + overflow hidden + flex-shrink for
single-line behavior. Add data-tab-panel-wide opt-out for full-width
tab panels (default 70ch).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

modules/helpdesk/pages/helpdesk/software-products/_form.phtml

@@ -26,7 +26,7 @@ $handoverSchemaFields = is_array($handoverSchemaFields ?? null) ? $handoverSchem
       </fieldset>
     </div>
 
-    <div data-tab-panel="handover-protocol">
+    <div data-tab-panel="handover-protocol" data-tab-panel-wide>
       <div class="handover-schema-split">
         <div class="handover-schema-split-editor">
           <div