Fix PR babysitter review comment monitoring (#16363)

## Summary
- prioritize newly surfaced review comments ahead of CI and mergeability
handling in the PR babysitter watcher
- keep `--watch` running for open PRs even when they are currently
merge-ready so later review feedback is not missed

.codex/skills/babysit-pr/scripts/test_gh_pr_watch.py

@@ -0,0 +1,155 @@
+import argparse
+import importlib.util
+from pathlib import Path
+
+import pytest
+
+
+MODULE_PATH = Path(__file__).with_name("gh_pr_watch.py")
+MODULE_SPEC = importlib.util.spec_from_file_location("gh_pr_watch", MODULE_PATH)
+gh_pr_watch = importlib.util.module_from_spec(MODULE_SPEC)
+assert MODULE_SPEC.loader is not None
+MODULE_SPEC.loader.exec_module(gh_pr_watch)
+
+
+def sample_pr():
+    return {
+        "number": 123,
+        "url": "https://github.com/openai/codex/pull/123",
+        "repo": "openai/codex",
+        "head_sha": "abc123",
+        "head_branch": "feature",
+        "state": "OPEN",
+        "merged": False,
+        "closed": False,
+        "mergeable": "MERGEABLE",
+        "merge_state_status": "CLEAN",
+        "review_decision": "",
+    }
+
+
+def sample_checks(**overrides):
+    checks = {
+        "pending_count": 0,
+        "failed_count": 0,
+        "passed_count": 12,
+        "all_terminal": True,
+    }
+    checks.update(overrides)
+    return checks
+
+
+def test_collect_snapshot_fetches_review_items_before_ci(monkeypatch, tmp_path):
+    call_order = []
+    pr = sample_pr()
+
+    monkeypatch.setattr(gh_pr_watch, "resolve_pr", lambda *args, **kwargs: pr)
+    monkeypatch.setattr(gh_pr_watch, "load_state", lambda path: ({}, True))
+    monkeypatch.setattr(
+        gh_pr_watch,
+        "get_authenticated_login",
+        lambda: call_order.append("auth") or "octocat",
+    )
+    monkeypatch.setattr(
+        gh_pr_watch,
+        "fetch_new_review_items",
+        lambda *args, **kwargs: call_order.append("review") or [],
+    )
+    monkeypatch.setattr(
+        gh_pr_watch,
+        "get_pr_checks",
+        lambda *args, **kwargs: call_order.append("checks") or [],
+    )
+    monkeypatch.setattr(
+        gh_pr_watch,
+        "summarize_checks",
+        lambda checks: call_order.append("summarize") or sample_checks(),
+    )
+    monkeypatch.setattr(
+        gh_pr_watch,
+        "get_workflow_runs_for_sha",
+        lambda *args, **kwargs: call_order.append("workflow") or [],
+    )
+    monkeypatch.setattr(
+        gh_pr_watch,
+        "failed_runs_from_workflow_runs",
+        lambda *args, **kwargs: call_order.append("failed_runs") or [],
+    )
+    monkeypatch.setattr(
+        gh_pr_watch,
+        "recommend_actions",
+        lambda *args, **kwargs: call_order.append("recommend") or ["idle"],
+    )
+    monkeypatch.setattr(gh_pr_watch, "save_state", lambda *args, **kwargs: None)
+
+    args = argparse.Namespace(
+        pr="123",
+        repo=None,
+        state_file=str(tmp_path / "watcher-state.json"),
+        max_flaky_retries=3,
+    )
+
+    gh_pr_watch.collect_snapshot(args)
+
+    assert call_order.index("review") < call_order.index("checks")
+    assert call_order.index("review") < call_order.index("workflow")
+
+
+def test_recommend_actions_prioritizes_review_comments():
+    actions = gh_pr_watch.recommend_actions(
+        sample_pr(),
+        sample_checks(failed_count=1),
+        [{"run_id": 99}],
+        [{"kind": "review_comment", "id": "1"}],
+        0,
+        3,
+    )
+
+    assert actions == [
+        "process_review_comment",
+        "diagnose_ci_failure",
+        "retry_failed_checks",
+    ]
+
+
+def test_run_watch_keeps_polling_open_ready_to_merge_pr(monkeypatch):
+    sleeps = []
+    events = []
+    snapshot = {
+        "pr": sample_pr(),
+        "checks": sample_checks(),
+        "failed_runs": [],
+        "new_review_items": [],
+        "actions": ["ready_to_merge"],
+        "retry_state": {
+            "current_sha_retries_used": 0,
+            "max_flaky_retries": 3,
+        },
+    }
+
+    monkeypatch.setattr(
+        gh_pr_watch,
+        "collect_snapshot",
+        lambda args: (snapshot, Path("/tmp/codex-babysit-pr-state.json")),
+    )
+    monkeypatch.setattr(
+        gh_pr_watch,
+        "print_event",
+        lambda event, payload: events.append((event, payload)),
+    )
+
+    class StopWatch(Exception):
+        pass
+
+    def fake_sleep(seconds):
+        sleeps.append(seconds)
+        if len(sleeps) >= 2:
+            raise StopWatch
+
+    monkeypatch.setattr(gh_pr_watch.time, "sleep", fake_sleep)
+
+    with pytest.raises(StopWatch):
+        gh_pr_watch.run_watch(argparse.Namespace(poll_seconds=30))
+
+    assert sleeps == [30, 30]
+    assert [event for event, _ in events] == ["snapshot", "snapshot"]