fix(client): validate active browser endpoints

- Check Unix socket reachability with a real connection attempt instead of treating any existing path as active.
- Report ambiguous host-only remote aliases with actionable --remote/--browser examples.
- Update client tests to use listening Unix sockets and cover ambiguous remote alias errors.
- Bump package and extension versions to 0.10.2.

extension/manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "browser-cli",
-  "version": "0.10.1",
+  "version": "0.10.2",
   "description": "Control your browser from the terminal or Python SDK",
   "permissions": [
     "tabs",