openDiff Does Not Call onEditorClose for GUI Editors

## Description

In `openDiff`, terminal-based editors correctly call `onEditorClose()` in a `finally` block.
However, GUI-based editors (e.g., VS Code, Cursor) never call `onEditorClose()`, causing inconsistent cleanup behavior and potential resource leaks.

### Location

* **File:** `packages/core/src/utils/editor.ts`
