Avoid SMB rename checks on the UI thread

The rename completion path in MainActivityHelper re-checked success by calling newFile.exists(context) on the UI thread because SAF-backed renames can report false negatives. For SMB targets that fallback routes into HybridFile.exists() and performs synchronous network I/O on the main thread. Limit the fallback probe to SAF-backed targets and cover it with a focused regression test.

Constraint: Preserve the post-rename verification workaround for SAF-backed rename targets
Rejected: Change HybridFile.exists() semantics for all SMB callers | too broad and would affect background operations that legitimately rely on it
Confidence: high
Scope-risk: narrow
Directive: Keep rename completion fallbacks off the UI thread for remote backends; only use exists(context) as a SAF-specific verification path
Tested: ./gradlew :app:testFdroidDebugUnitTest --tests com.amaze.filemanager.utils.MainActivityHelperTest -x kaptFdroidDebugUnitTestKotlin
Tested: ./gradlew :app:compileFdroidDebugJavaWithJavac
Tested: ./gradlew :app:compileFdroidDebugUnitTestJavaWithJavac -x kaptFdroidDebugUnitTestKotlin
Not-tested: Full :app:testFdroidDebugUnitTest (blocked by existing kaptFdroidDebugUnitTestKotlin failure in unrelated tests referencing missing ShadowMultiDex)

Author: venkyqz

app/src/main/java/com/amaze/filemanager/utils/MainActivityHelper.java

@@ -388,7 +388,9 @@ public void done(final HybridFile hFile, final boolean b) {
                    * DocumentFile.renameTo() may return false even when rename is successful. Hence we need an extra check
                    * instead of merely looking at the return value
                    */
-                  if (b || newFile.exists(context)) {
+                  if (b
+                      || ((newFile.isDocumentFile() || newFile.isOtgFile())
+                          && newFile.exists(context))) {
                     Intent intent = new Intent(MainActivity.KEY_INTENT_LOAD_LIST);
 
                     intent.putExtra(