fix(review): four findings from adversarial Codex review round 1

- twitter: align backend selection with the two-phase findings pattern —
  an unauthenticated twitter-cli (warn) no longer blocks a fully-working
  OpenCLI (ok) further down the candidate list
- watch: use _is_newer_version like check-update (the != comparison kept
  the downgrade prompt this branch fixed elsewhere)
- uninstall: third copy of the skill-dir removal also gets the symlink
  guard (full `agent-reach uninstall` path)
- doctor: a stale active_backend from a previous check on the singleton
  channel no longer leaks into an errored result

+4 regression tests (162 total).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_cli.py

@@ -199,3 +199,26 @@ class TestVersionCompare:
     def test_unparseable_falls_back_to_inequality(self):
         assert cli._is_newer_version("2026.06-beta", "1.5.0") is True
         assert cli._is_newer_version("1.5.0", "1.5.0-dev") is True
+
+
+class TestWatchVersionCompare:
+    def test_watch_does_not_prompt_downgrade(self, monkeypatch, capsys):
+        """watch 与 check-update 同语义:本地领先远端 release 时不提示更新。"""
+        class R:
+            status_code = 200
+            headers = {}
+
+            @staticmethod
+            def json():
+                return {"tag_name": "v1.4.2", "body": ""}
+
+        monkeypatch.setattr(cli, "_github_get_with_retry", lambda *a, **k: (R(), None, 1))
+        monkeypatch.setattr(
+            "agent_reach.doctor.check_all",
+            lambda config: {"web": {"status": "ok", "name": "任意网页", "message": "ok",
+                            "tier": 0, "backends": ["Jina Reader"], "active_backend": "Jina Reader"}},
+        )
+        cli._cmd_watch()
+        out = capsys.readouterr().out
+        assert "新版本可用" not in out
+        assert "全部正常" in out