feat: add Firefox extension support

- Add Firefox as an install target with native messaging manifest support.
- Generate Firefox-specific extension packages with Gecko metadata and AMO-compatible manifest transforms.
- Keep tab group commands available in Firefox through dynamic tab group API helpers.
- Avoid Firefox linter warnings for static tab group API references and direct eval tokens.
- Add Firefox packaging and installer regression coverage.
- Bump the package and extension version to 0.15.1.

extension/src/commands/session-snapshot.ts

@@ -1,4 +1,4 @@
-import { normalizeGroupColor } from '../core';
+import { normalizeGroupColor, queryTabGroups } from '../core';
 import type { SessionTab, StoredSession } from '../types';
 
 export function buildSessionSnapshot(tabs: chrome.tabs.Tab[], groups: chrome.tabGroups.TabGroup[]): SessionTab[] {
@@ -28,7 +28,7 @@ export function buildSessionSnapshot(tabs: chrome.tabs.Tab[], groups: chrome.tab
  */
 export async function captureCurrentSession(): Promise<{ session: StoredSession; signature: string; tabCount: number }> {
   const tabs = await chrome.tabs.query({});
-  const groups = await chrome.tabGroups.query({});
+  const groups = await queryTabGroups({});
   const sessionTabs = buildSessionSnapshot(tabs, groups);
   const signature = sessionSignature(sessionTabs);
   const session: StoredSession = {