test(hooks): finalize mutation test improvements and release acceptance

- Raise use-swipe-gesture mutation score to 66.13% (target 65%+)
- Maintain use-reduced-motion mutation score at 76.32% (target 50%+)
- Fix use-reduced-motion.ts ESLint set-state-in-effect warning
- Add UJ-10 deep searcher journey (category browse → article read → content discovery)
- Add 40 new test files (analytics, detail, sections, ui, lib components)
- Update test-strategy-plan.md to v2.0 (sync test count to 1591)
- Sync README.md with final release metrics

Quality gates: TS 0 errors, ESLint 0 errors, 121 suites / 1591 tests passed

src/components/ui/sonner.test.tsx

@@ -0,0 +1,41 @@
+// @ts-nocheck
+import { describe, it, expect, jest } from '@jest/globals';
+import { render } from '@testing-library/react';
+import '@testing-library/jest-dom';
+
+// Mock sonner Toaster
+jest.mock('sonner', () => ({
+  Toaster: ({ theme, className, ...props }: any) => (
+    <div data-testid="sonner-toaster" data-theme={theme} className={className} {...props} />
+  ),
+  toast: {
+    success: jest.fn(),
+    error: jest.fn(),
+    info: jest.fn(),
+  },
+}));
+
+// Mock lucide-react icons used by Toaster
+jest.mock('lucide-react', () => ({
+  CheckCircle2: (props: any) => <svg data-testid="icon-check-circle" {...props} />,
+  AlertCircle: (props: any) => <svg data-testid="icon-alert-circle" {...props} />,
+  Info: (props: any) => <svg data-testid="icon-info" {...props} />,
+  X: (props: any) => <svg data-testid="icon-x" {...props} />,
+}));
+
+describe('Toaster', () => {
+  it('renders with correct className "toaster group"', () => {
+    const { Toaster } = require('./sonner');
+    const { container } = render(<Toaster />);
+    const toaster = container.querySelector('[data-testid="sonner-toaster"]');
+    expect(toaster).toBeInTheDocument();
+    expect(toaster).toHaveClass('toaster group');
+  });
+
+  it('passes theme="light" to sonner', () => {
+    const { Toaster } = require('./sonner');
+    const { container } = render(<Toaster />);
+    const toaster = container.querySelector('[data-testid="sonner-toaster"]');
+    expect(toaster).toHaveAttribute('data-theme', 'light');
+  });
+});