fix(design): bound requests and prevent mutation replay

tests/unit/proxy-fetch.test.ts

@@ -35,6 +35,36 @@ describe('proxyAwareFetch', () => {
     expect(net.fetch).toHaveBeenCalledWith('https://example.test', undefined);
   });
 
+  it('does not replay a mutation through global fetch after Electron net.fetch fails', async () => {
+    setElectronVersion('43.4.0');
+    const transportError = new Error('response transport failed');
+    const fetchMock = vi.fn();
+    vi.mocked(net.fetch).mockRejectedValue(transportError);
+    vi.stubGlobal('fetch', fetchMock);
+
+    await expect(proxyAwareFetch('https://example.test/quote', {
+      method: 'PATCH',
+      body: JSON.stringify({ aspect_ratio: '16:9' }),
+    })).rejects.toBe(transportError);
+
+    expect(net.fetch).toHaveBeenCalledOnce();
+    expect(fetchMock).not.toHaveBeenCalled();
+  });
+
+  it('retains the global fallback for safe reads after Electron net.fetch fails', async () => {
+    setElectronVersion('43.4.0');
+    const response = new Response('node fallback');
+    const fetchMock = vi.fn().mockResolvedValue(response);
+    vi.mocked(net.fetch).mockRejectedValue(new Error('electron transport failed'));
+    vi.stubGlobal('fetch', fetchMock);
+
+    await expect(proxyAwareFetch('https://example.test/read', {
+      method: 'GET',
+    })).resolves.toBe(response);
+
+    expect(fetchMock).toHaveBeenCalledWith('https://example.test/read', { method: 'GET' });
+  });
+
   it('uses the global fetch outside Electron', async () => {
     setElectronVersion(undefined);
     const response = new Response('node');