feat(renderer): Minimap (custom overview, wired to settings.minimap)

tests/component/editor/Minimap.test.tsx

@@ -0,0 +1,20 @@
+import { describe, it, expect } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import { Minimap } from '@/components/editor/Minimap';
+
+describe('Minimap', () => {
+  it('renders lines of content as shrunk text', () => {
+    const content = 'line 1\nline 2\nline 3';
+    render(<Minimap content={content} />);
+    const lines = screen.getAllByTestId('minimap-line');
+    expect(lines).toHaveLength(3);
+  });
+
+  it('renders a viewport indicator', () => {
+    render(
+      <Minimap content={'line 1\nline 2\nline 3'} scrollRatio={0.5} visibleRatio={0.5} />
+    );
+    const indicator = screen.getByTestId('minimap-viewport');
+    expect(indicator).toBeInTheDocument();
+  });
+});