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

.agents/skills/lib_py/delegation/registry.py

@@ -90,6 +90,7 @@ def register_job(
     transport: str = "herdr",
     supersede_older_attempt: bool = False,
     parent_job: Optional[str] = None,
+    dry_run: bool = False,
 ) -> str:
     """Create a new ``pending`` job record and return its id.
 
@@ -106,6 +107,10 @@ def register_job(
 
     Issue #34: ``parent_job`` names the job this one was delegated from, so a
     loop waiting on the parent can find and wait for it. None is a root job.
+
+    Issue #50 (review 1e25cf2f F1): ``dry_run`` marks the record of a
+    ``submit --dry-run``, which is never dispatched, so the registry admission
+    does not count it as an open job of its session.
     """
     job_id = job_id or generate_job_id(bits)
     heartbeat_sec = max(1, int(heartbeat_sec))
@@ -152,6 +157,8 @@ def register_job(
         # Issue #34: the job this one was delegated from (None = a root job)
         "parent_job": parent_job,
     }
+    if dry_run:
+        record["dry_run"] = True
     with registry_lock(registry_dir):
         if mqtt_common._job_path(job_id, registry_dir).exists():
             if not supersede_older_attempt:
@@ -393,6 +400,8 @@ def _build_parser() -> argparse.ArgumentParser:
     p_reg.add_argument("--reviewer", default=None)
     p_reg.add_argument("--reviewer-session", default=None)
     p_reg.add_argument("--max-iterations", type=int, default=5)
+    p_reg.add_argument("--dry-run", action="store_true",
+                       help="the record of a submit --dry-run: never dispatched, not an open job for admission")
     p_reg.add_argument("--parent-job", default=None,
                        help="the job this one is delegated from (Issue #34); must exist in this registry")
 
@@ -569,6 +578,7 @@ def main(argv: Optional[List[str]] = None) -> int:
             attempt_id=args.attempt_id,
             job_id=args.job_id,
             parent_job=args.parent_job,
+            dry_run=args.dry_run,
         )
         print(job_id)
         return 0