feat: first cut at the full renderer

tests/renderer/components/Panel.test.tsx

@@ -234,4 +234,39 @@ describe('Panel', () => {
 
     expect(screen.getByRole('tab', { name: 'Output' })).toHaveAttribute('aria-selected', 'true');
   });
+
+  it('renders grouped tasks as expandable parent rows with child task names in tasks tab', async () => {
+    useAppStore.setState({
+      tasks: [
+        {
+          taskId: 'site-render-core-1',
+          name: 'Render Site Core',
+          status: 'running',
+          progress: 42,
+          message: 'Generating root pages...',
+          startTime: '2026-02-20T10:00:00.000Z',
+          groupId: 'site-render-1',
+          groupName: 'Render Site',
+        },
+        {
+          taskId: 'site-render-tag-1',
+          name: 'Render Tag Archives',
+          status: 'pending',
+          progress: 0,
+          message: 'Waiting to start...',
+          startTime: '2026-02-20T10:00:01.000Z',
+          groupId: 'site-render-1',
+          groupName: 'Render Site',
+        },
+      ] as any,
+    });
+
+    render(<Panel />);
+
+    const parent = screen.getByRole('button', { name: 'Render Site (2)' });
+    expect(parent).toBeInTheDocument();
+    expect(await screen.findByText('Render Site Core')).toBeInTheDocument();
+    expect(screen.getByText('Render Tag Archives')).toBeInTheDocument();
+    expect(screen.getByText('42%')).toBeInTheDocument();
+  });
 });

tests/renderer/components/TaskPopup.test.tsx

@@ -0,0 +1,78 @@
+import React from 'react';
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { fireEvent, render, screen } from '@testing-library/react';
+import { TaskPopup } from '../../../src/renderer/components/TaskPopup/TaskPopup';
+import { useAppStore } from '../../../src/renderer/store';
+import type { TaskProgress } from '../../../src/main/shared/electronApi';
+
+function makeTask(overrides: Partial<TaskProgress> = {}): TaskProgress {
+  return {
+    taskId: overrides.taskId ?? 'task-1',
+    status: overrides.status ?? 'running',
+    progress: overrides.progress ?? 10,
+    message: overrides.message ?? 'Running task',
+    startTime: overrides.startTime ?? '2026-02-20T10:00:00.000Z',
+    endTime: overrides.endTime,
+    error: overrides.error,
+    groupId: overrides.groupId,
+    groupName: overrides.groupName,
+  };
+}
+
+describe('TaskPopup grouped tasks', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    useAppStore.setState({
+      tasks: [],
+    });
+  });
+
+  it('shows grouped render tasks and expands to list child tasks', () => {
+    useAppStore.setState({
+      tasks: [
+        makeTask({
+          taskId: 'site-render-core-1',
+          status: 'running',
+          message: 'Generating root pages',
+          groupId: 'site-render-1',
+          groupName: 'Render Site',
+        }),
+        makeTask({
+          taskId: 'site-render-date-1',
+          status: 'running',
+          message: 'Generating date archive pages',
+          groupId: 'site-render-1',
+          groupName: 'Render Site',
+        }),
+      ],
+    });
+
+    render(<TaskPopup />);
+
+    fireEvent.click(screen.getByRole('button', { name: /running/i }));
+
+    const groupToggle = screen.getByRole('button', { name: /Render Site \(2\)/i });
+    expect(groupToggle).toBeInTheDocument();
+    expect(screen.getByText('Generating root pages')).toBeInTheDocument();
+    expect(screen.getByText('Generating date archive pages')).toBeInTheDocument();
+
+    fireEvent.click(groupToggle);
+
+    expect(screen.queryByText('Generating root pages')).not.toBeInTheDocument();
+    expect(screen.queryByText('Generating date archive pages')).not.toBeInTheDocument();
+  });
+
+  it('continues to render ungrouped tasks directly', () => {
+    useAppStore.setState({
+      tasks: [
+        makeTask({ taskId: 'ungrouped-1', status: 'running', message: 'Standalone task' }),
+      ],
+    });
+
+    render(<TaskPopup />);
+
+    fireEvent.click(screen.getByRole('button', { name: /running/i }));
+
+    expect(screen.getByText('Standalone task')).toBeInTheDocument();
+  });
+});