feat(frontend): hydrate + debounced-persist cross-subject plot config

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/tests/ExperimentAnalysisCharts.test.jsx

@@ -1,5 +1,5 @@
 import React from 'react';
-import { render, screen, fireEvent } from '@testing-library/react';
+import { render, screen, fireEvent, act } from '@testing-library/react';
 
 // recharts uses ResizeObserver (absent in jsdom); stub all used pieces as passthroughs.
 // Coverage boundary: with recharts mocked out, these tests cover only the sidebar
@@ -59,3 +59,68 @@ it('unchecking a subject in the sidebar persists across re-render', () => {
   expect(screen.getByLabelText('Mouse-A1').checked).toBe(false);
   expect(screen.getByText('Show all')).toBeInTheDocument();
 });
+
+it('hydrates hidden subjects and sidebar-open from plotConfig', () => {
+  render(
+    <ExperimentAnalysisCharts
+      animals={ANIMALS}
+      experimentStatuses={STATUSES}
+      subjectTemplate={SUBJECT_TEMPLATE}
+      dailyTemplate={DAILY_TEMPLATE}
+      plotConfig={{ hiddenSubjects: ['a1'], sidebarOpen: true }}
+    />,
+  );
+  expect(screen.getByLabelText('Mouse-A1').checked).toBe(false);
+  expect(screen.getByLabelText('Mouse-B1').checked).toBe(true);
+});
+
+describe('debounced auto-save', () => {
+  beforeEach(() => jest.useFakeTimers());
+  afterEach(() => jest.useRealTimers());
+
+  it('does not call onPersistConfig on initial render', () => {
+    const onPersist = jest.fn();
+    render(
+      <ExperimentAnalysisCharts
+        animals={ANIMALS} experimentStatuses={STATUSES}
+        subjectTemplate={SUBJECT_TEMPLATE} dailyTemplate={DAILY_TEMPLATE}
+        plotConfig={null} onPersistConfig={onPersist}
+      />,
+    );
+    act(() => { jest.advanceTimersByTime(1500); });
+    expect(onPersist).not.toHaveBeenCalled();
+  });
+
+  it('calls onPersistConfig ~1s after a change, with the updated config', () => {
+    const onPersist = jest.fn().mockResolvedValue({});
+    render(
+      <ExperimentAnalysisCharts
+        animals={ANIMALS} experimentStatuses={STATUSES}
+        subjectTemplate={SUBJECT_TEMPLATE} dailyTemplate={DAILY_TEMPLATE}
+        plotConfig={{ sidebarOpen: true }} onPersistConfig={onPersist}
+      />,
+    );
+    fireEvent.click(screen.getByLabelText('Mouse-A1'));
+    expect(onPersist).not.toHaveBeenCalled();
+    act(() => { jest.advanceTimersByTime(1100); });
+    expect(onPersist).toHaveBeenCalledTimes(1);
+    expect(onPersist.mock.calls[0][0].hiddenSubjects).toContain('a1');
+  });
+
+  it('does not save and clears the saving hint when a change is reverted before the debounce fires', () => {
+    const onPersist = jest.fn().mockResolvedValue({});
+    render(
+      <ExperimentAnalysisCharts
+        animals={ANIMALS} experimentStatuses={STATUSES}
+        subjectTemplate={SUBJECT_TEMPLATE} dailyTemplate={DAILY_TEMPLATE}
+        plotConfig={{ sidebarOpen: true }} onPersistConfig={onPersist}
+      />,
+    );
+    fireEvent.click(screen.getByLabelText('Mouse-A1')); // hide a1
+    expect(screen.getByText('Saving…')).toBeInTheDocument();
+    fireEvent.click(screen.getByLabelText('Mouse-A1')); // revert before the 1s timer
+    act(() => { jest.advanceTimersByTime(1100); });
+    expect(onPersist).not.toHaveBeenCalled();
+    expect(screen.queryByText('Saving…')).toBeNull();
+  });
+});