feat(issue-50): create --onboard waits for the onboarding job to end (A)

The handshake only said the agent saw the prompt (#23). create_session.sh
now waits, after `started`, for the onboarding job to reach a terminal
status and makes that its own result, so the orchestrator learns it from
create's exit (MULTI_AGENT_RULES §6) instead of guessing from herdr's
agent_status:

- lib_py/delegation/wrapper.py: `wait-terminal` (completed|error|cancelled,
  `timeout` after --timeout, `missing` when the record is gone; stops with
  its caller via --watch-pid) and `onboard-exit` (completed 0, error or
  cancelled 44, timeout or missing 45). bash branches on the printed answer.
- lib.sh: delegate_wait_terminal / delegate_onboard_exit, thin calls.
- create_session.sh: `onboarding completed: job <id> (<n>s)` on stdout, or
  `last_visible_status: onboarding-<status>` on the row, the reason on stderr
  and `exit 44` / `exit 45` after `trap - EXIT` - the session is kept, as for
  a missing handshake. The "no started" path (error, exit 0 before) now ends
  with 44. MAM_ONBOARD_WAIT_S (default 600, floor 1) bounds the wait.
- worktree_prepare.sh: 44/45 pass through with "session and worktree kept".
- create SKILL.md exit table (44, 45) and the knob; the #42 inventory follows.
- tests/conftest.py: --onboard is the default, so ~60 sandbox create tests
  reach the new wait. The mock herdr now acts as the agent for create's
  onboarding prompt - it runs the publish commands the prompt names through
  the real publish_event.py - and MAM_ONBOARD_WAIT_S=3 caps a test that turns
  that off (MAM_MOCK_ONBOARD_HANDSHAKE=0 -> 44, `started` -> 45). The
  delegate-job wrapper's prompt has another shape and is never answered.
- tests/test_issue50_onboard.py: the decision tables, create in the sandbox
  (0 / 44 / 45, session kept, row note, trap window), the knob's integer
  rule, worktree_prepare's pass-through.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

.agents/skills/lib_py/delegation/wrapper.py

@@ -18,6 +18,12 @@ no answer) cannot pass for "no". The wrapper uses --print.
   finalize-begin / finalize-end ...          finalize_unfinished, split around the one
                                              herdr diagnostic probe bash still runs
 
+Issue #50 (create --onboard waits for the onboarding to end):
+  wait-terminal --job J --registry-dir R --timeout T [--watch-pid P]
+                                             prints the job's terminal status, or
+                                             `timeout` / `missing`
+  onboard-exit <status>                      create's exit code for it: 0, 44, 45
+
 finalize-end answers on fd 3 (stdout when fd 3 is closed): its stdout carries
 registry.py's close output to the wrapper's stdout, as before. It runs as a
 child of the wrapper and must not outlive it (review R1): with --watch-pid it
@@ -48,6 +54,10 @@ SUB_RC_COMPLETED, SUB_RC_ERROR, SUB_RC_NO_EVENT, SUB_RC_BROKER_UNAVAILABLE, SUB_
 
 TERMINAL = ("completed", "error", "cancelled")
 EXIT_CODES = {"completed": 0, "error": 1, "timeout": 2, "broker_unavailable": 3, "cancelled": 5}
+# Issue #50: create --onboard's exit code for how the onboarding job ended.
+# 44 = the agent ended it with error (or it was cancelled), 45 = it did not end
+# within MAM_ONBOARD_WAIT_S (or its record is gone). The session is kept either way.
+ONBOARD_EXIT_CODES = {"completed": 0, "error": 44, "cancelled": 44, "timeout": 45, "missing": 45}
 
 
 def _now() -> int:
@@ -169,6 +179,30 @@ def _tail(path: str, n: int) -> List[str]:
         return fh.read().splitlines()[-n:]
 
 
+# ---------------------------------------------------------------------------
+# Issue #50 A: create --onboard waits for the onboarding job to end
+# ---------------------------------------------------------------------------
+
+def onboard_exit(status: str) -> int:
+    return ONBOARD_EXIT_CODES.get(status, 45)
+
+
+def wait_terminal(a: argparse.Namespace) -> str:
+    """The job's terminal status once it has one; `timeout` after --timeout s,
+    `missing` when the record is gone. Reads the disk every second."""
+    deadline = _now() + a.timeout
+    record = os.path.join(a.registry_dir, f"{a.job}.json")
+    while True:
+        disk = disk_status(a.registry_dir, a.job)
+        if disk in TERMINAL:
+            return disk
+        if not os.path.isfile(record):
+            return "missing"
+        if _now() >= deadline:
+            return "timeout"
+        _sleep(a, 1)
+
+
 def finalize_begin(a: argparse.Namespace) -> str:
     """`keep` (FINAL_JOB_STATUS untouched), `done <final>`, or
     `go|probe <final> <evidence_until> <deadline>`."""
@@ -307,6 +341,12 @@ def _parser() -> argparse.ArgumentParser:
     s.add_argument("session")
     s.add_argument("agent")
     s.add_argument("--print", action="store_true", help="print yes/no and exit 0")
+    s = sub.add_parser("wait-terminal")
+    s.add_argument("--job", required=True)
+    s.add_argument("--registry-dir", required=True)
+    s.add_argument("--timeout", type=int, required=True)
+    s.add_argument("--watch-pid", type=int, default=None, help="the caller's pid; gone -> stop waiting")
+    sub.add_parser("onboard-exit").add_argument("status")
     for name in ("finalize-begin", "finalize-end"):
         s = sub.add_parser(name)
         s.add_argument("--job", required=True)
@@ -353,6 +393,13 @@ def main(argv: Optional[List[str]] = None) -> int:
         return _yes_no(stall_watch(a.session, a.agent), a.print)
     elif a.cmd == "finalize-begin":
         print(finalize_begin(a))
+    elif a.cmd == "wait-terminal":
+        try:
+            print(wait_terminal(a))
+        except OwnerGone:
+            print(f"wait-terminal: caller pid {a.watch_pid} is gone; stopped waiting on job {a.job}", file=sys.stderr)
+    elif a.cmd == "onboard-exit":
+        print(onboard_exit(a.status))
     else:
         try:
             _answer(finalize_end(a))