fix(update): an unlistable jobs directory refuses; the rowless-agent hint names its server (Issue #72, review R2, R3)

R2: glob() hid a listing error, so an unreadable .mam/jobs (or MAM_JOBS_DIR,
or another row's jobs dir) counted as empty and the update installed over an
open job. Records are now listed with os.listdir; a directory that cannot be
listed, or stat'ed, is a blocker with its path.

R3: a discovered agent with no row was told to run stop with --session only;
stop then looked on the workspace's server, not the one the agent was found
on. The hint now carries --herdr-session <server>, quoted.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_issue72_update.py

@@ -45,6 +45,15 @@ elif a[:2] == ["agent", "list"]:
     if spec.get("fail") == "agent-list:" + server:
         sys.exit(1)
     print(json.dumps({"result": {"agents": spec.get("agents", {}).get(server, [])}}))
+elif a[:2] == ["agent", "get"]:
+    hit = [x for x in spec.get("agents", {}).get(server, []) if a[2] in (x.get("name"), x.get("pane_id"))]
+    if not hit:
+        sys.exit(1)
+    print(json.dumps({"result": {"agent": hit[0]}}))
+elif a[:2] == ["pane", "close"]:
+    spec.setdefault("agents", {})[server] = [x for x in spec.get("agents", {}).get(server, [])
+                                             if x.get("pane_id") != a[2]]
+    json.dump(spec, open(os.environ["FAKE_HERDR_SPEC"], "w"))
 '''
 
 STUB_MONITOR = r'''#!/usr/bin/env bash
@@ -366,6 +375,28 @@ def test_refuses_a_rowless_agent_on_any_running_server(box):
     assert '"down"' not in calls
 
 
+def test_the_rowless_agent_hint_stops_it_on_the_server_it_was_found_on(box):
+    """R3: the printed stop command names the server; without it stop looks on
+    the workspace's server, where a same-named agent runs outside the workspace."""
+    write_rows(box.ws, [])
+    box.herdr(sessions={"default": True, "unrecorded-server": True},
+              agents={"unrecorded-server": [{"name": "stray", "pane_id": "w3:p1", "cwd": str(box.ws / "sub")}],
+                      "default": [{"name": "stray", "pane_id": "w1:p1", "cwd": str(box.root / "elsewhere")}]})
+    res = box.update()
+    assert res.returncode == 1, res.stdout + res.stderr
+    line = next(ln for ln in res.stderr.splitlines() if "herdr agent stray" in ln)
+    cmd = line.split("stop it: ", 1)[1]
+    assert "--herdr-session unrecorded-server" in cmd, cmd
+    stop = subprocess.run(["bash", "-c", cmd], cwd=str(box.ws), env=box.env, stdin=subprocess.DEVNULL,
+                          capture_output=True, text=True, timeout=120)
+    assert stop.returncode == 0, stop.stdout + stop.stderr
+    agents = json.loads(box.spec.read_text())["agents"]
+    assert agents["unrecorded-server"] == []
+    assert [x["pane_id"] for x in agents["default"]] == ["w1:p1"], "the same name elsewhere is left alone"
+    res = box.update()
+    assert res.returncode == 0, res.stdout + res.stderr
+
+
 def test_an_agent_outside_the_workspace_does_not_refuse(box):
     box.herdr(agents={"default": [{"name": "other", "pane_id": "w1:p2", "cwd": str(box.root / "elsewhere")}]})
     res = box.update()
@@ -406,6 +437,34 @@ def test_open_jobs_refuse_and_terminal_or_dry_run_do_not(box, tmp_path):
     del box.env["MAM_JOBS_DIR"]
 
 
+@pytest.mark.skipif(os.geteuid() == 0, reason="root reads a mode-000 directory")
+def test_a_jobs_directory_that_cannot_be_listed_refuses(box, tmp_path):
+    """R2: an unreadable .mam/jobs (or MAM_JOBS_DIR under an unreadable parent)
+    is not an empty registry."""
+    jobs = box.mam / "jobs"
+    write_job(jobs, "hidden1", status="running")
+    before = snapshot(box.ws)
+    jobs.chmod(0)
+    try:
+        res = box.update()
+    finally:
+        jobs.chmod(0o755)
+    assert_refused_unchanged(box, before, res, "jobs directory %s cannot be listed" % jobs)
+    (jobs / "hidden1.json").unlink()
+
+    parent = tmp_path / "locked"
+    write_job(parent / "jobs", "env1", status="running")
+    box.env["MAM_JOBS_DIR"] = str(parent / "jobs")
+    before = snapshot(box.ws)
+    parent.chmod(0)
+    try:
+        res = box.update()
+    finally:
+        parent.chmod(0o755)
+    assert_refused_unchanged(box, before, res, "jobs directory %s cannot be listed" % (parent / "jobs"))
+    del box.env["MAM_JOBS_DIR"]
+
+
 def test_other_control_planes_count_only_jobs_addressed_to_this_registry(box, tmp_path):
     other = tmp_path / "other-plane" / "jobs"
     write_job(other, "theirs", status="running", session="herdr:not-ours")