fix(settings): move the data-dir baseline after a successful save

The settings page no longer unmounts after saving, but the saved
app-config-dir baseline was only captured on mount. After saving a new
data directory and choosing "restart later" the save button stayed,
resetting to the old value could not be saved, and every later save
reported "restart required" again. Keep the baseline in state and commit
it to the just-saved value once the override is persisted.

tests/hooks/useDirectorySettings.test.tsx

@@ -170,6 +170,27 @@ describe("useDirectorySettings", () => {
     });
   });
 
+  it("moves the saved baseline when a new app config dir is committed", async () => {
+    getAppConfigDirOverrideMock.mockResolvedValue("/override/app");
+    const { result } = renderHook(() =>
+      useDirectorySettings({
+        settings: createSettings(),
+        onUpdateSettings: vi.fn(),
+      }),
+    );
+    await waitFor(() =>
+      expect(result.current.initialAppConfigDir).toBe("/override/app"),
+    );
+
+    act(() => result.current.commitAppConfigDir("/saved/app"));
+    expect(result.current.initialAppConfigDir).toBe("/saved/app");
+
+    // 重置回的也是新基准
+    act(() => result.current.updateAppConfigDir("/typed/app"));
+    act(() => result.current.resetAllDirectories());
+    expect(result.current.appConfigDir).toBe("/saved/app");
+  });
+
   it("updates app config directory via browseAppConfigDir", async () => {
     selectConfigDirectoryMock.mockResolvedValue("  /new/app  ");
 

tests/hooks/useSettings.test.tsx

@@ -123,6 +123,7 @@ const createDirectorySettingsMock = (
   },
   isLoading: false,
   initialAppConfigDir: undefined,
+  commitAppConfigDir: vi.fn(),
   updateDirectory: vi.fn(),
   updateAppConfigDir: vi.fn(),
   browseDirectory: vi.fn(),
@@ -297,6 +298,10 @@ describe("useSettings hook", () => {
     });
 
     expect(saveResult).toEqual({ requiresRestart: true });
+    // 存完把基准值换成刚存的，保存按钮和下一次「需要重启」只跟新改动走
+    expect(directorySettingsMock.commitAppConfigDir).toHaveBeenCalledWith(
+      "/override/app",
+    );
     expect(mutateAsyncMock).toHaveBeenCalledTimes(1);
     const payload = mutateAsyncMock.mock.calls[0][0] as Settings;
     expect(payload.claudeConfigDir).toBe("/custom/claude");