feat(mcp): target DOM tools by tab

- Add server-side search filtering to the MCP tabs_list tool.
- Let MCP DOM query, click, and type tools operate on an explicit tab_id.
- Use tab-scoped DOM eval fallbacks when the SDK active-tab helpers are not enough.
- Cover tab filtering and tab-targeted DOM operations in MCP tests.
- Bump package and extension versions to 0.16.8 and refresh the lockfile.

extension/manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "browser-cli",
-  "version": "0.16.7",
+  "version": "0.16.8",
   "description": "Control your browser from the terminal or Python SDK",
   "browser_specific_settings": {
     "gecko": {