Fix flaky FileSearchTests.testBinaryContentTypeWithDescriber race condition

The test was failing intermittently (1 out of 3 runs) due to a race
condition in content type registration. The test dynamically registers
a binary content type but files were created and searched before the
content type was fully available, causing the binary file to be
incorrectly included in search results.

This fix adds:
1. Explicit wait loop to verify content type is registered before
   proceeding (up to 500ms with 10ms intervals)
2. Force content type detection on files after creation by calling
   getContentDescription() to ensure binary signature describer is
   properly applied

Verified with 5 consecutive test runs - all passed.

🤖 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

@@ -35,6 +35,8 @@
 import org.eclipse.core.runtime.IContributor;
 import org.eclipse.core.runtime.IExtensionRegistry;
 import org.eclipse.core.runtime.Platform;
+import org.eclipse.core.runtime.content.IContentType;
+import org.eclipse.core.runtime.content.IContentTypeManager;
 
 import org.eclipse.core.resources.IFile;
 import org.eclipse.core.resources.IFolder;
@@ -601,12 +603,31 @@ private void testBinaryContentTypeWithDescriber(TestResultCollector collector) t
 						.forEach(extension -> registry.removeExtension(extension, masterToken));
 			}) {
 
+				// Wait for content type to be registered and available
+				// This prevents race conditions where the content type might not be immediately available
+				IContentTypeManager contentTypeManager= Platform.getContentTypeManager();
+				IContentType binaryContentType= null;
+				for (int i= 0; i < 50 && binaryContentType == null; i++) {
+					binaryContentType= contentTypeManager.getContentType("org.eclipse.search.tests.binaryFile");
+					if (binaryContentType == null) {
+						Thread.sleep(10); // Wait 10ms before retrying
+					}
+				}
+				if (binaryContentType == null) {
+					throw new AssertionError("Content type 'org.eclipse.search.tests.binaryFile' was not registered");
+				}
+
 				// 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");
 
+				// Force content type detection on files to ensure the newly registered content type is applied
+				// This helps avoid race conditions where the content type might not be immediately available
+				textfile.getContentDescription();
+				binaryfile.getContentDescription();
+
 				Pattern searchPattern= PatternConstructor.createPattern("hello", true, false);
 
 				// Search only in the unique folder to avoid interference from other tests