fix: add backwards compatibility for PluginDocumentSettingPanel

The original change imported PluginDocumentSettingPanel from
@wordpress/editor to resolve a deprecation warning in WordPress 6.6+.
However, this component only exists in @wordpress/editor from WordPress
6.6 onwards; in WordPress 6.4-6.5 it remains in @wordpress/edit-post.

This implements a runtime fallback pattern that checks wp.editor first
(WordPress 6.6+) and falls back to wp.editPost (WordPress 6.4-6.5),
maintaining compatibility across the supported WordPress version range
whilst eliminating the deprecation warning in newer versions.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: GaryJones

src/__tests__/plugin-document-setting-panel.test.js

@@ -0,0 +1,66 @@
+/**
+ * Tests for PluginDocumentSettingPanel backwards compatibility.
+ *
+ * The component moved from @wordpress/edit-post to @wordpress/editor in WP 6.6.
+ * We use a runtime fallback to support both WP 6.4-6.5 (edit-post) and WP 6.6+ (editor).
+ */
+
+describe( 'PluginDocumentSettingPanel compatibility', () => {
+	const MockComponent = () => 'MockPluginDocumentSettingPanel';
+
+	beforeEach( () => {
+		// Reset the wp global before each test
+		global.wp = {};
+	} );
+
+	afterEach( () => {
+		// Clean up
+		delete global.wp;
+	} );
+
+	it( 'should use wp.editor.PluginDocumentSettingPanel when available (WP 6.6+)', () => {
+		global.wp = {
+			editor: {
+				PluginDocumentSettingPanel: MockComponent,
+			},
+			editPost: {
+				PluginDocumentSettingPanel: () => 'OldComponent',
+			},
+		};
+
+		const PluginDocumentSettingPanel =
+			wp.editor?.PluginDocumentSettingPanel ||
+			wp.editPost?.PluginDocumentSettingPanel;
+
+		expect( PluginDocumentSettingPanel ).toBe( MockComponent );
+	} );
+
+	it( 'should fall back to wp.editPost.PluginDocumentSettingPanel (WP 6.4-6.5)', () => {
+		global.wp = {
+			editor: {},
+			editPost: {
+				PluginDocumentSettingPanel: MockComponent,
+			},
+		};
+
+		const PluginDocumentSettingPanel =
+			wp.editor?.PluginDocumentSettingPanel ||
+			wp.editPost?.PluginDocumentSettingPanel;
+
+		expect( PluginDocumentSettingPanel ).toBe( MockComponent );
+	} );
+
+	it( 'should handle wp.editor being undefined (WP 6.4-6.5)', () => {
+		global.wp = {
+			editPost: {
+				PluginDocumentSettingPanel: MockComponent,
+			},
+		};
+
+		const PluginDocumentSettingPanel =
+			wp.editor?.PluginDocumentSettingPanel ||
+			wp.editPost?.PluginDocumentSettingPanel;
+
+		expect( PluginDocumentSettingPanel ).toBe( MockComponent );
+	} );
+} );

src/index.js

@@ -2,10 +2,15 @@
  * WordPress dependencies
  */
 import { registerPlugin } from '@wordpress/plugins';
-import { PluginDocumentSettingPanel } from '@wordpress/editor';
 import { __ } from '@wordpress/i18n';
 import { select, subscribe } from "@wordpress/data";
 
+// PluginDocumentSettingPanel moved from @wordpress/edit-post to @wordpress/editor in WP 6.6.
+// Use fallback for backwards compatibility with WP 6.4-6.5.
+const PluginDocumentSettingPanel =
+	wp.editor?.PluginDocumentSettingPanel ||
+	wp.editPost?.PluginDocumentSettingPanel;
+
 /**
  * Components
  */