test: add comprehensive tests for v4 features

Add unit tests for sidebar manager, command palette, print preview,
main process utilities, and markdown extensions. Update jest config
to exclude untestable Electron-specific files from coverage and
raise coverage thresholds.

tests/command-palette.test.js

@@ -0,0 +1,144 @@
+/**
+ * @jest-environment jsdom
+ */
+
+/**
+ * Tests for CommandPalette
+ * Tests command registration, filtering, execution, and keyboard navigation
+ */
+
+describe('CommandPalette', () => {
+    let CommandPalette;
+
+    beforeEach(() => {
+        document.body.innerHTML = `
+            <div class="command-palette-overlay hidden" id="command-palette-overlay">
+                <div class="command-palette">
+                    <input type="text" id="command-palette-input">
+                    <div id="command-palette-results"></div>
+                </div>
+            </div>
+        `;
+        CommandPalette = require('../src/command-palette').CommandPalette;
+    });
+
+    test('starts hidden', () => {
+        const palette = new CommandPalette();
+        expect(palette.isOpen()).toBe(false);
+    });
+
+    test('opens and focuses input', () => {
+        const palette = new CommandPalette();
+        palette.open();
+        expect(palette.isOpen()).toBe(true);
+    });
+
+    test('closes', () => {
+        const palette = new CommandPalette();
+        palette.open();
+        palette.close();
+        expect(palette.isOpen()).toBe(false);
+    });
+
+    test('registers and renders commands', () => {
+        const palette = new CommandPalette();
+        palette.register('Test Command', 'Ctrl+T', () => {});
+        palette.register('Another Command', '', () => {});
+        palette.open();
+        const items = document.querySelectorAll('.command-item');
+        expect(items.length).toBe(2);
+    });
+
+    test('filters commands by search', () => {
+        const palette = new CommandPalette();
+        palette.register('Save File', 'Ctrl+S', () => {});
+        palette.register('Open File', 'Ctrl+O', () => {});
+        palette.register('Bold Text', 'Ctrl+B', () => {});
+        palette.renderResults('file');
+        const items = document.querySelectorAll('.command-item');
+        expect(items.length).toBe(2);
+    });
+
+    test('executes command', () => {
+        const palette = new CommandPalette();
+        const action = jest.fn();
+        palette.register('Test', '', action);
+        palette.open();
+        palette.executeSelected();
+        expect(action).toHaveBeenCalled();
+    });
+
+    test('highlights matching text', () => {
+        const palette = new CommandPalette();
+        const result = palette.highlightMatch('Save File', 'save');
+        expect(result).toContain('<strong>');
+        expect(result).toContain('Save');
+    });
+
+    test('highlightMatch returns original text when no query', () => {
+        const palette = new CommandPalette();
+        const result = palette.highlightMatch('Save File', '');
+        expect(result).toBe('Save File');
+    });
+
+    test('filters case-insensitively', () => {
+        const palette = new CommandPalette();
+        palette.register('Save File', '', () => {});
+        palette.register('Open File', '', () => {});
+        palette.renderResults('SAVE');
+        const items = document.querySelectorAll('.command-item');
+        expect(items.length).toBe(1);
+    });
+
+    test('shows all commands when query is empty', () => {
+        const palette = new CommandPalette();
+        palette.register('Cmd1', '', () => {});
+        palette.register('Cmd2', '', () => {});
+        palette.register('Cmd3', '', () => {});
+        palette.renderResults('');
+        const items = document.querySelectorAll('.command-item');
+        expect(items.length).toBe(3);
+    });
+
+    test('displays shortcut when provided', () => {
+        const palette = new CommandPalette();
+        palette.register('Save File', 'Ctrl+S', () => {});
+        palette.open();
+        const shortcut = document.querySelector('.command-shortcut');
+        expect(shortcut).not.toBeNull();
+        expect(shortcut.textContent).toBe('Ctrl+S');
+    });
+
+    test('does not display shortcut when empty', () => {
+        const palette = new CommandPalette();
+        palette.register('Test Command', '', () => {});
+        palette.open();
+        const shortcut = document.querySelector('.command-shortcut');
+        expect(shortcut).toBeNull();
+    });
+
+    test('closes on overlay click', () => {
+        const palette = new CommandPalette();
+        palette.open();
+        // Simulate click on the overlay itself
+        const event = new Event('click', { bubbles: true });
+        Object.defineProperty(event, 'target', { value: palette.overlay });
+        palette.overlay.dispatchEvent(event);
+        expect(palette.isOpen()).toBe(false);
+    });
+
+    test('executeSelected does nothing when no commands', () => {
+        const palette = new CommandPalette();
+        palette.open();
+        // Should not throw
+        expect(() => palette.executeSelected()).not.toThrow();
+    });
+
+    test('closes after executing command', () => {
+        const palette = new CommandPalette();
+        palette.register('Test', '', jest.fn());
+        palette.open();
+        palette.executeSelected();
+        expect(palette.isOpen()).toBe(false);
+    });
+});