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.ts

@@ -1,4 +1,4 @@
-import { getLargeOperationThrottle, getProfileAlias, getSessionTabs, getSessions, normalizeGroupColor, runLargeOperation, throwIfJobCancelled, updateJobProgress, yieldForLargeOperation } from '../core';
+import { getLargeOperationThrottle, getProfileAlias, getSessionTabs, getSessions, groupTabs, normalizeGroupColor, runLargeOperation, throwIfJobCancelled, updateJobProgress, updateTabGroup, yieldForLargeOperation } from '../core';
 import { CommandGroup } from '../classes/CommandGroup';
 import { AutoSaveManager } from './autosave';
 import { captureCurrentSession } from './session-snapshot';
@@ -91,8 +91,8 @@ export class SessionCommands extends CommandGroup {
       updateJobProgress(__job, { phase: "restoring groups", current: 0, total: groups.size });
       for (const { meta, tabIds } of groups.values()) {
         throwIfJobCancelled(__job);
-        const restoredGroupId = await chrome.tabs.group({ tabIds });
-        await chrome.tabGroups.update(restoredGroupId, {
+        const restoredGroupId = await groupTabs({ tabIds });
+        await updateTabGroup(restoredGroupId, {
           title: meta.title || "",
           color: normalizeGroupColor(meta.color),
           collapsed: Boolean(meta.collapsed),