fix(tests): add requestAnimationFrame fallback for flaky Ubuntu CI tests

Add defensive runtime check in useXterm.ts to handle test environments
where requestAnimationFrame may not be defined. This fixes intermittent
CI failures on Ubuntu where the vitest node/jsdom environment switching
caused a race condition.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/frontend/src/renderer/components/terminal/useXterm.ts

@@ -219,8 +219,13 @@ export function useXterm({ terminalId, onCommandEnter, onResize, onDimensionsRea
 
     // Use requestAnimationFrame to wait for layout, then fit
     // This is more reliable than a fixed timeout
+    // Fallback to setTimeout for test environments where requestAnimationFrame may not be defined
+    const raf = typeof requestAnimationFrame !== 'undefined'
+      ? requestAnimationFrame
+      : (cb: FrameRequestCallback) => setTimeout(() => cb(Date.now()), 0) as unknown as number;
+
     const performInitialFit = () => {
-      requestAnimationFrame(() => {
+      raf(() => {
         if (fitAddonRef.current && xtermRef.current && terminalRef.current) {
           // Check if container has valid dimensions
           const rect = terminalRef.current.getBoundingClientRect();