fix(issue-50): review findings of PR #56 on macOS

- admission: a `submit --dry-run` record is marked dry_run and is not an
  open job of its session (review 1e25cf2f F1)
- create: the monitor-row adoption requires the row's server to be the one
  this create spawned on (review 1e25cf2f F2)
- pane lock: retry only on contention (BlockingIOError); the docs say the
  flock lasts while any fd-9 holder (the claim shell and the shim) lives
  (review 66680d9d)
- tests on macOS: real-herdr box HOMEs under /tmp (sun_path is 104 bytes),
  resolved paths, the fake claude reads non-canonical input (MAX_CANON 1024)
  and the pane is read unwrapped; lock holders exec their sleep so killing
  them frees the lock; the adoption tests name the server

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VCgu9Fa9iT7TbJUSzdq4Ff

tests/test_issue50_dispatch.py

@@ -159,6 +159,26 @@ def test_u1c_the_job_itself_and_unreadable_records_are_skipped(tmp_path):
     assert decide.open_jobs(str(tmp_path), "herdr:s", me) == ([], [])
 
 
+def test_u1e_a_dry_run_record_is_not_an_open_job(tmp_path):
+    """review 1e25cf2f F1: `submit --dry-run` registers a record it never
+    dispatches; it stays pending (Issue #34 shows it as an open job), but the
+    admission must not wait for it."""
+    reg = tmp_path / "jobs"
+    env = dict(os.environ, HOME=str(tmp_path), MAM_ENV_FILE=str(tmp_path / ".mam.env.absent"))
+    res = subprocess.run(["bash", str(WRAPPER), "submit", "--agent", "human", "--agent-session", "herdr:s",
+                          "--dry-run", "--registry-dir", str(reg), "--prompt", "preview only"],
+                         capture_output=True, text=True, env=env, cwd=str(tmp_path), timeout=120)
+    assert res.returncode == 0, res.stdout + res.stderr
+    (dry,) = [p.stem for p in reg.glob("*.json")]
+    assert _rec(reg, dry)["status"] == "pending" and _rec(reg, dry)["dry_run"] is True
+    me = _register(reg)
+    assert decide.open_jobs(str(reg), "herdr:s", me) == ([], [])
+    assert decide.wait_open_jobs(_ns(reg, me)) == "clear"
+    # control: the same record without the mark is an `injected` job that holds the session
+    _edit(reg, dry, dry_run=None)
+    assert decide.wait_open_jobs(_ns(reg, me)) == f"busy {dry}"
+
+
 # ---------------------------------------------------------------------------
 # U2 - FIFO release and the bound (wait_s=0: an immediate decision)
 # ---------------------------------------------------------------------------