feat(extension): add Firefox WebExtension support

- Add a neutral WebExtension API adapter that uses Firefox browser.* or Chromium chrome.* without mutating globals.
- Switch extension runtime code to the adapter and add Firefox-specific typings for tabs, windows, tab groups, storage, scripting, and native messaging ports.
- Fix Firefox temporary add-on instructions to load the packaged manifest with background.scripts instead of the Chromium service worker manifest.
- Detect Firefox in clients.list via runtime.getBrowserInfo and keep Chromium user-agent fallback support.
- Make navigate.open wait briefly for Firefox to replace initial about:blank with the requested URL.
- Add JS coverage for API selection, clients.list browser detection, and Firefox navigate.open URL polling.
- Bump package and extension version to 0.15.2.

extension/test/navigation.test.ts

@@ -0,0 +1,66 @@
+// @ts-nocheck
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { NavigationCommands } from '../src/commands/navigation';
+import { JobManager } from '../src/classes/JobManager';
+import { makeChromeMock } from './chrome-mock';
+
+function makeNavigationCommands() {
+  return new NavigationCommands({ jobs: new JobManager() });
+}
+
+test('navigate.open waits until Firefox updates about:blank to the requested URL', async () => {
+  const originalChrome = globalThis.chrome;
+  const originalBrowser = globalThis.browser;
+  const originalNavigator = globalThis.navigator;
+  const firefoxApi = makeChromeMock();
+  const targetUrl = 'https://example.com/?browser-cli-firefox-open-wait=1';
+  let getCalls = 0;
+
+  try {
+    delete globalThis.chrome;
+    globalThis.browser = {
+      ...firefoxApi,
+      runtime: {
+        getManifest: () => ({ version: '0.15.1' }),
+        getBrowserInfo: async () => ({ name: 'Firefox', vendor: 'Mozilla', version: '151.0.2', buildID: 'test' }),
+      },
+      tabs: {
+        ...firefoxApi.tabs,
+        create: async () => ({ id: 123, windowId: 1, index: 0, active: true, groupId: -1, url: 'about:blank' }),
+        get: async () => {
+          getCalls += 1;
+          return {
+            id: 123,
+            windowId: 1,
+            index: 0,
+            active: true,
+            groupId: -1,
+            url: getCalls < 2 ? 'about:blank' : targetUrl,
+          };
+        },
+      },
+    };
+    Object.defineProperty(globalThis, 'navigator', {
+      value: { platform: 'test-platform', userAgent: 'Mozilla/5.0 Firefox/151.0.2' },
+      configurable: true,
+    });
+
+    const result = await makeNavigationCommands().commands['navigate.open']({ url: targetUrl, focus: true });
+
+    assert.equal(result.id, 123);
+    assert.equal(result.url, targetUrl);
+    assert.ok(getCalls >= 2);
+  } finally {
+    if (originalChrome === undefined) delete globalThis.chrome;
+    else globalThis.chrome = originalChrome;
+
+    if (originalBrowser === undefined) delete globalThis.browser;
+    else globalThis.browser = originalBrowser;
+
+    Object.defineProperty(globalThis, 'navigator', {
+      value: originalNavigator,
+      configurable: true,
+    });
+  }
+});