feat: upgrade design system to v0.1.19, use onNavigate/fillHeight, add SonarQube workflow

- Use Sidebar onNavigate callback instead of display:contents click interception
- Use DataTable fillHeight prop instead of manual scroll wrapper divs
- Fix DataTable scroll/pagination by adding overflow:hidden to content container
- Fix left panel in split view to use flex column instead of overflow:auto
- Make error tab stack trace scrollable for large traces
- Add nightly SonarQube workflow with manual trigger support

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/ExecutionDiagram/ExecutionDiagram.module.css

@@ -447,6 +447,11 @@
   overflow-y: auto;
 }
 
+.errorStackWrap pre {
+  max-height: 50vh;
+  overflow-y: auto;
+}
+
 .errorStackLabel {
   font-size: 10px;
   font-weight: 600;

ui/src/components/ExecutionDiagram/tabs/ErrorTab.tsx

@@ -38,7 +38,9 @@ export function ErrorTab({ processor, executionDetail }: ErrorTabProps) {
       {errorStackTrace && (
         <>
           <div className={styles.errorStackLabel}>Stack Trace</div>
-          <CodeBlock content={errorStackTrace} copyable />
+          <div className={styles.errorStackWrap}>
+            <CodeBlock content={errorStackTrace} copyable />
+          </div>
         </>
       )}
     </div>