Feature/ai post suggestions (#40)

* feat: first cut on ai suggestion system for title and summary

* feat: completion of titling/excerpt/slug-suggestion AI quick action

* feat: feeds use existing excerpts. also documentation.

---------

Co-authored-by: hugo <hugoms@me.com>

tests/renderer/components/EditorMetadataCollapse.test.tsx

@@ -229,4 +229,37 @@ describe('Editor metadata collapse', () => {
     });
     expect(container.querySelector('.editor-header-row')).toBeNull();
   });
+
+  it('keeps excerpt panel collapsed by default and toggles it independently', async () => {
+    (window as any).electronAPI.posts.get = vi.fn().mockResolvedValue(createPost({ title: '' }));
+
+    const { container } = render(<PostEditor postId="post-1" />);
+
+    await act(async () => {
+      await Promise.resolve();
+      await Promise.resolve();
+      await Promise.resolve();
+    });
+
+    expect(container.querySelector('.editor-header-row')).not.toBeNull();
+    expect(container.querySelector('.editor-excerpt-panel')).toBeNull();
+
+    const excerptToggle = Array.from(container.querySelectorAll('.metadata-toggle')).find((node) =>
+      node.textContent?.includes('Excerpt')
+    );
+    expect(excerptToggle).not.toBeNull();
+    expect(excerptToggle?.classList.contains('expanded')).toBe(false);
+
+    await act(async () => {
+      fireEvent.click(excerptToggle!);
+    });
+
+    expect(container.querySelector('.editor-excerpt-panel')).not.toBeNull();
+
+    await act(async () => {
+      fireEvent.click(excerptToggle!);
+    });
+
+    expect(container.querySelector('.editor-excerpt-panel')).toBeNull();
+  });
 });