Don't sync the selection from a rich text edited inside another host

When a rich text is itself focused but nested inside another editing host
(e.g. an HTML block's static inner blocks), writing flow owns its selection.
Return early from the selection change handler in that case, matching the
focus handler, so the permanently subscribed listener does not fight writing
flow over the caret. The editable root host case is unaffected: there the
host holds focus, not the element.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: ellatrix

packages/rich-text/src/hook/event-listeners/input-and-selection.js

@@ -142,6 +142,17 @@ export default ( props ) => ( element ) => {
 			return;
 		}
 
+		// When this element is itself focused but nested inside another
+		// editing host (e.g. an HTML block's static inner blocks), writing
+		// flow owns its selection; don't self-sync. The editable root host
+		// case is different: the host holds focus, not this element.
+		if (
+			ownerDocument.activeElement === element &&
+			element.parentElement.closest( '[contenteditable="true"]' )
+		) {
+			return;
+		}
+
 		// In case of a keyboard event, ignore selection changes during
 		// composition.
 		if ( isComposing ) {