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/multi-agent-mux-delegate-job/multi-agent-mux-delegate-job

@@ -292,6 +292,10 @@ cmd_submit() {
     fi
   fi
 
+  # Issue #50: a dry-run's record is never dispatched, so admission skips it
+  local reg_dry=()
+  if [[ "$DRY_RUN" == "1" ]]; then reg_dry=(--dry-run); fi
+
   # 1) register job (prints the new job id)
   JOB_ID="$("$PY" "$SCRIPT_DIR/scripts/registry.py" --registry-dir "$REGISTRY_DIR" register \
       "${reg_prompt[@]}" --agent "$AGENT" --agent-session "$AGENT_SESSION" --role "$DELEGATE_ROLE" \
@@ -299,7 +303,7 @@ cmd_submit() {
       --heartbeat-sec "$HEARTBEAT_SEC" --heartbeat-misses "$HEARTBEAT_MISSES" --ack-timeout "$ACK_TIMEOUT" \
       --transport "$(_is_remote "$AGENT_SESSION" && echo remote || echo herdr)" \
       --job-type "$TYPE" --reviewer "$REVIEWER" --reviewer-session "$REVIEWER_SESSION" \
-      --max-iterations "$MAX_ITERATIONS" ${reg_parent[@]+"${reg_parent[@]}"})"
+      --max-iterations "$MAX_ITERATIONS" ${reg_parent[@]+"${reg_parent[@]}"} ${reg_dry[@]+"${reg_dry[@]}"})"
   echo "registered job: $JOB_ID"
 
   # 1-1) Provision job directory and write direct brief.md (MAM Job Restructuring)