Fix flaky QuickAccessComputerTest by waiting for async search results

The test was failing intermittently because QuickSearchQuickAccessComputer
performs asynchronous background searches with a 200ms timeout. On slower
CI systems (particularly macOS), this timeout was insufficient, causing
the test to fail when it checked for results before the search completed.

This fix:
- Saves the Display reference before closing the dialog to avoid NPE
- Wraps the QuickAccessComputer result check in DisplayHelper.waitForCondition
  with a 5-second timeout, retrying if no results are found initially
- Allows the background search job sufficient time to find matches

The test now passes consistently across multiple runs.

Fixes #3042

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: vogella

tests/org.eclipse.text.quicksearch.tests/src/org/eclipse/text/quicksearch/tests/QuickAccessComputerTest.java

@@ -9,7 +9,6 @@
  *******************************************************************************/
 package org.eclipse.text.quicksearch.tests;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.io.IOException;
@@ -55,8 +54,16 @@ void testQuickAccessComputer() throws CoreException, IOException {
 		dialog.setInitialPattern(request);
 		dialog.setBlockOnOpen(false);
 		dialog.open();
-		assertTrue(DisplayHelper.waitForCondition(dialog.getShell().getDisplay(), 2000, () -> dialog.getResult().length > 0));
+		var display = dialog.getShell().getDisplay();
+		assertTrue(DisplayHelper.waitForCondition(display, 2000, () -> dialog.getResult().length > 0));
 		dialog.close();
-		assertEquals(1, new QuickSearchQuickAccessComputer().computeElements(request, new NullProgressMonitor()).length);
+
+		// Wait for the QuickAccessComputer to return results, as the search happens asynchronously.
+		// Retry the search if it initially returns no results, allowing time for the background
+		// search job to find matches. This addresses race conditions on slower CI systems.
+		assertTrue(DisplayHelper.waitForCondition(display, 5000, () -> {
+			QuickSearchQuickAccessComputer computer = new QuickSearchQuickAccessComputer();
+			return computer.computeElements(request, new NullProgressMonitor()).length == 1;
+		}), "Expected QuickAccessComputer to find exactly one result within timeout");
 	}
 }