feat(monospace): add get/set IPC handlers with safe validation

tests/unit/main/monospace/monospace-handlers.test.js

@@ -0,0 +1,57 @@
+const { EventEmitter } = require('events');
+
+class FakeIpcMain extends EventEmitter {
+  constructor() {
+    super();
+    this.handlers = new Map();
+  }
+  handle(channel, handler) {
+    this.handlers.set(channel, handler);
+  }
+}
+
+describe('monospace-handlers', () => {
+  let ipc;
+  let register;
+  let store;
+
+  beforeEach(() => {
+    jest.resetModules();
+    ipc = new FakeIpcMain();
+    store = new Map();
+    jest.doMock('electron', () => ({ ipcMain: ipc }));
+    jest.doMock('../../../../src/main/store', () => ({
+      get: (k, d) => (store.has(k) ? store.get(k) : d),
+      set: (k, v) => store.set(k, v),
+    }));
+    ({ register } = require('../../../../src/main/ipc/monospace-handlers'));
+  });
+
+  test('get-monospace-settings returns defaults when nothing stored', () => {
+    register();
+    const handler = ipc.handlers.get('get-monospace-settings');
+    return Promise.resolve(handler({})).then((result) => {
+      expect(result).toEqual({ monospaceFont: 'jetbrains-mono', monospaceLigatures: false });
+    });
+  });
+
+  test('set-monospace-settings persists and returns sanitized values', () => {
+    register();
+    const handler = ipc.handlers.get('set-monospace-settings');
+    return Promise.resolve(
+      handler({}, { monospaceFont: 'fira-code', monospaceLigatures: 1 })
+    ).then((result) => {
+      expect(result).toEqual({ monospaceFont: 'fira-code', monospaceLigatures: true });
+      expect(store.get('monospaceFont')).toBe('fira-code');
+      expect(store.get('monospaceLigatures')).toBe(true);
+    });
+  });
+
+  test('set-monospace-settings rejects invalid font key', () => {
+    register();
+    const handler = ipc.handlers.get('set-monospace-settings');
+    return Promise.resolve(handler({}, { monospaceFont: 'comic-sans' })).then((result) => {
+      expect(result.monospaceFont).toBe('jetbrains-mono');
+    });
+  });
+});