fix(iOS): removing chars during IME composition (#674)

# Summary
Fixes: #673 

## Test Plan

Run reproduction steps from #673 
the issue should be resolved.

## Screenshots / Videos


https://github.com/user-attachments/assets/b41de743-0652-4d2d-bd8a-62db9c403f8e


## Compatibility

| OS      | Implemented |
| ------- | :---------: |
| iOS     |    ✅     |
| Android |    ❌     |
| Web     |    ❌     |

## Checklist

- [X] E2E tests are passing
- [ ] Required E2E tests have been added (if applicable)

---------

Co-authored-by: Mikołaj Szydłowski <9szydlowski9@gmail.com>

Author: kacperzolkiewski

ios/EnrichedTextInputView.mm

@@ -1662,8 +1662,9 @@ - (void)handleWordModificationBasedChanges:(NSString *)word
 }
 
 - (void)anyTextMayHaveBeenModified {
-  // we don't do no text changes when working with iOS marked text
+  // we don't do text changes when working with iOS marked text
   if (textView.markedTextRange != nullptr) {
+    [self handlePlaceholderVisibility];
     return;
   }
 
@@ -1685,13 +1686,7 @@ - (void)anyTextMayHaveBeenModified {
     [mentionStyleClass manageMentionEditing];
   }
 
-  // placholder management
-  if (!_placeholderLabel.hidden && textView.textStorage.string.length > 0) {
-    [self setPlaceholderLabelShown:NO];
-  } else if (textView.textStorage.string.length == 0 &&
-             _placeholderLabel.hidden) {
-    [self setPlaceholderLabelShown:YES];
-  }
+  [self handlePlaceholderVisibility];
 
   // modified words handling
   NSArray *currentDirtyRanges = [attributesManager getDirtyRanges];
@@ -1747,6 +1742,16 @@ - (void)anyTextMayHaveBeenModified {
   [self scheduleRelayoutIfNeeded];
 }
 
+- (void)handlePlaceholderVisibility {
+  // placeholder management
+  if (!_placeholderLabel.hidden && textView.textStorage.string.length > 0) {
+    [self setPlaceholderLabelShown:NO];
+  } else if (textView.textStorage.string.length == 0 &&
+             _placeholderLabel.hidden) {
+    [self setPlaceholderLabelShown:YES];
+  }
+}
+
 // Debounced relayout helper - coalesces multiple requests into one per runloop
 // tick
 - (void)scheduleRelayoutIfNeeded {

ios/utils/ParagraphAttributesUtils.mm

@@ -20,6 +20,13 @@ + (BOOL)handleBackspaceInRange:(NSRange)range
     return NO;
   }
 
+  // Do not manually intervene if the user is in the middle of IME
+  // composition. Let the iOS system handle the backspace natively to prevent
+  // state desync.
+  if (typedInput->textView.markedTextRange != nullptr) {
+    return NO;
+  }
+
   // we make sure it was a backspace (text with 0 length) and it deleted
   // something (range longer than 0)
   if (text.length > 0 || range.length == 0) {