Fix flaky test FileSearchTests.testBinaryContentTypeWithDescriber

The test was failing intermittently on Windows with "expected: <1> but
was: <2>" because it was searching the entire project scope where files
from other concurrent tests could interfere.

Changes:
- Use unique timestamped folder name to avoid conflicts
- Narrow search scope to only the test's specific folder
- Add comments explaining the fix

This ensures test isolation when running in parallel.

Fixes #3490

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

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

Author: vogella

tests/org.eclipse.search.tests/src/org/eclipse/search/tests/filesearch/FileSearchTests.java

@@ -601,13 +601,16 @@ private void testBinaryContentTypeWithDescriber(TestResultCollector collector) t
 						.forEach(extension -> registry.removeExtension(extension, masterToken));
 			}) {
 
-				IFolder folder= ResourceHelper.createFolder(fProject.getFolder("folder1"));
+				// Use unique folder name to avoid conflicts with other tests running in parallel
+				String uniqueFolderName= "binaryContentTypeTest-" + java.util.UUID.randomUUID().toString();
+				IFolder folder= ResourceHelper.createFolder(fProject.getFolder(uniqueFolderName));
 				IFile textfile= ResourceHelper.createFile(folder, "textfile", "text hello");
 				IFile binaryfile= ResourceHelper.createFile(folder, "binaryfile", "binary hello");
 
 				Pattern searchPattern= PatternConstructor.createPattern("hello", true, false);
 
-				FileTextSearchScope scope= FileTextSearchScope.newSearchScope(new IResource[] { fProject }, (String[]) null, false);
+				// Search only in the unique folder to avoid interference from other tests
+				FileTextSearchScope scope= FileTextSearchScope.newSearchScope(new IResource[] { folder }, (String[]) null, false);
 				TextSearchEngine.create().search(scope, collector, searchPattern, null);
 
 				TestResult[] results= collector.getResults();