feat: Blocker Resolution View - Answer Agent Questions (#333)

## Summary
Implements #333: Blocker Resolution View — a dedicated page for responding to
agent questions and unblocking stuck tasks.

- New `/blockers` route with inline answer forms and SWR polling (5s)
- Sidebar notification badge showing open blocker count (10s polling)
- Collapsible resolved blockers section with answer history
- Shared `formatRelativeTime` utility
- Full accessibility support (ARIA, keyboard nav, Cmd+Enter)
- 29 new tests (15 BlockerCard + 14 ResolvedBlockersSection)

## Acceptance Criteria
- [x] List all open blockers with task context
- [x] Blocker question prominently displayed
- [x] Shows timestamp metadata
- [x] Inline answer form (text area + submit)
- [x] Submit answer auto-resumes task execution
- [x] Option to skip/cancel blocker (with re-expand)
- [x] Collapsed section for resolved blockers
- [x] Notification badge count on sidebar icon
- [x] Full context view (task ID + question)

## Validation
- Tests: 332 passing (29 suites)
- Linting: Clean
- Code review: 3 rounds, all feedback addressed
- Build: Compiles successfully

Closes #333

Author: frankbria

web-ui/__mocks__/@hugeicons/react.js

@@ -51,5 +51,6 @@ module.exports = {
   WifiDisconnected01Icon: createIconMock('WifiDisconnected01Icon'),
   SidebarLeftIcon: createIconMock('SidebarLeftIcon'),
   ArrowDown01Icon: createIconMock('ArrowDown01Icon'),
+  ArrowUp01Icon: createIconMock('ArrowUp01Icon'),
   StopIcon: createIconMock('StopIcon'),
 };

web-ui/__tests__/components/blockers/BlockerCard.test.tsx

@@ -0,0 +1,220 @@
+import { render, screen, waitFor } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { BlockerCard } from '@/components/blockers/BlockerCard';
+import { blockersApi } from '@/lib/api';
+import type { Blocker } from '@/types';
+
+// Mock the API
+jest.mock('@/lib/api', () => ({
+  blockersApi: {
+    answer: jest.fn(),
+  },
+}));
+
+const mockAnswer = blockersApi.answer as jest.MockedFunction<typeof blockersApi.answer>;
+
+function makeBlocker(overrides: Partial<Blocker> = {}): Blocker {
+  return {
+    id: 'blocker-1',
+    workspace_id: 'ws-1',
+    task_id: 'task-42',
+    question: 'Which database should we use?',
+    answer: null,
+    status: 'OPEN',
+    created_at: new Date(Date.now() - 30 * 60 * 1000).toISOString(), // 30m ago
+    answered_at: null,
+    ...overrides,
+  };
+}
+
+describe('BlockerCard', () => {
+  const workspacePath = '/home/user/project';
+  const onAnswered = jest.fn();
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+    jest.useFakeTimers();
+  });
+
+  afterEach(() => {
+    jest.useRealTimers();
+  });
+
+  it('renders the blocker question prominently', () => {
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    expect(screen.getByText('Which database should we use?')).toBeInTheDocument();
+  });
+
+  it('displays the task ID', () => {
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    expect(screen.getByText('Task task-42')).toBeInTheDocument();
+  });
+
+  it('shows OPEN badge', () => {
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    expect(screen.getByText('OPEN')).toBeInTheDocument();
+  });
+
+  it('shows relative timestamp', () => {
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    expect(screen.getByText('30m ago')).toBeInTheDocument();
+  });
+
+  it('shows the answer form for OPEN blockers', () => {
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    expect(screen.getByTestId('blocker-answer-form')).toBeInTheDocument();
+    expect(screen.getByPlaceholderText('Type your answer...')).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /answer blocker/i })).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /skip/i })).toBeInTheDocument();
+  });
+
+  it('disables submit button when answer is empty', () => {
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    expect(screen.getByRole('button', { name: /answer blocker/i })).toBeDisabled();
+  });
+
+  it('enables submit button when answer has text', async () => {
+    jest.useRealTimers();
+    const user = userEvent.setup();
+
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    const textarea = screen.getByPlaceholderText('Type your answer...');
+    await user.type(textarea, 'Use PostgreSQL');
+
+    expect(screen.getByRole('button', { name: /answer blocker/i })).toBeEnabled();
+  });
+
+  it('shows success state after successful submission', async () => {
+    jest.useRealTimers();
+    const user = userEvent.setup();
+    mockAnswer.mockResolvedValueOnce(makeBlocker({ status: 'ANSWERED', answer: 'Use PostgreSQL' }));
+
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    const textarea = screen.getByPlaceholderText('Type your answer...');
+    await user.type(textarea, 'Use PostgreSQL');
+    await user.click(screen.getByRole('button', { name: /answer blocker/i }));
+
+    await waitFor(() => {
+      expect(screen.getByText(/blocker answered/i)).toBeInTheDocument();
+    });
+  });
+
+  it('calls blockersApi.answer with correct arguments', async () => {
+    jest.useRealTimers();
+    const user = userEvent.setup();
+    mockAnswer.mockResolvedValueOnce(makeBlocker({ status: 'ANSWERED', answer: 'Use PostgreSQL' }));
+
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    const textarea = screen.getByPlaceholderText('Type your answer...');
+    await user.type(textarea, 'Use PostgreSQL');
+    await user.click(screen.getByRole('button', { name: /answer blocker/i }));
+
+    expect(mockAnswer).toHaveBeenCalledWith(workspacePath, 'blocker-1', 'Use PostgreSQL');
+  });
+
+  it('displays error when API call fails', async () => {
+    jest.useRealTimers();
+    const user = userEvent.setup();
+    mockAnswer.mockRejectedValueOnce({ detail: 'Blocker already resolved' });
+
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    const textarea = screen.getByPlaceholderText('Type your answer...');
+    await user.type(textarea, 'Some answer');
+    await user.click(screen.getByRole('button', { name: /answer blocker/i }));
+
+    await waitFor(() => {
+      expect(screen.getByText('Blocker already resolved')).toBeInTheDocument();
+    });
+  });
+
+  it('hides form when Skip is clicked and shows "Show answer form" button', async () => {
+    jest.useRealTimers();
+    const user = userEvent.setup();
+
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    await user.click(screen.getByRole('button', { name: /skip/i }));
+
+    expect(screen.queryByTestId('blocker-answer-form')).not.toBeInTheDocument();
+    expect(screen.getByRole('button', { name: /show answer form/i })).toBeInTheDocument();
+  });
+
+  it('re-expands form when "Show answer form" is clicked after Skip', async () => {
+    jest.useRealTimers();
+    const user = userEvent.setup();
+
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    await user.click(screen.getByRole('button', { name: /skip/i }));
+    await user.click(screen.getByRole('button', { name: /show answer form/i }));
+
+    expect(screen.getByTestId('blocker-answer-form')).toBeInTheDocument();
+  });
+
+  it('shows character count', async () => {
+    jest.useRealTimers();
+    const user = userEvent.setup();
+
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    expect(screen.getByText('0 characters')).toBeInTheDocument();
+
+    const textarea = screen.getByPlaceholderText('Type your answer...');
+    await user.type(textarea, 'Hello');
+
+    expect(screen.getByText('5 characters')).toBeInTheDocument();
+  });
+
+  it('has correct data-testid attributes', () => {
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    expect(screen.getByTestId('blocker-card')).toBeInTheDocument();
+    expect(screen.getByTestId('blocker-answer-form')).toBeInTheDocument();
+  });
+
+  it('has correct aria-label on textarea', () => {
+    render(
+      <BlockerCard blocker={makeBlocker()} workspacePath={workspacePath} onAnswered={onAnswered} />
+    );
+
+    expect(screen.getByLabelText('Your answer to the blocker question')).toBeInTheDocument();
+  });
+});