fix(issue-23): an unacknowledged onboarding marks the job and keeps the session

Two defects in the started-based verdict, both found by the full suite.

The first was destructive. No `started` within T exited 1, which fired the
rollback trap and killed the session. That is worse than the bug being fixed:
create_session already has a rule for "the agent is not responding but the
process is alive" one step earlier - a TUI that never signalled ready is
preserved for diagnosis - and an onboarding that is merely slow is the same
situation. The job is marked `error` and warned about loudly; the session, its
row and the pane stay. MULTI_AGENT_RULES §6 has the GM gate on this job
anyway, so an unacknowledged onboarding still blocks real work.

It also broke 21 tests across 8 modules (create/sanity/tier2/tier3/tier4/
issue15/issue19/issue21) and added roughly an hour to the suite: no sandbox
has an agent to publish `started`, so every create_session test sat out the
full 180 s and then failed on the rollback. MAM_ONBOARD_ACK_S shortens that
wait, and the sandbox fixture sets 3 s. It is deliberately not the wrapper's
MAM_INJECT_ACK_GRACE_S - that is a different wait whose own tests assert on
the value they pass, and reusing it made issue18's acceptance2 read "within
3s" instead of "within 4s".

The second: the delivery failure published `error` and then the rollback
published `cancelled` on the same job, which the registry refuses
("conflicting cancelled after terminal error"). Terminal events are published
exactly once, so the trap now skips a job this run already closed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/conftest.py

@@ -227,6 +227,12 @@ def mam_sandbox(tmp_path, monkeypatch, request):
     # (`reconcile.sh --subscribe --idle-timeout 0`) from a sandbox. Tests that
     # exercise the daemon itself override this with "0" or delenv.
     monkeypatch.setenv("MAM_NO_SUBSCRIBER_DAEMON", "1")
+    # Issue #23: onboarding delivery now waits for the agent's own `started`.
+    # No sandbox has a real agent to publish one, so without a short grace
+    # every create_session test would sit out the full 180 s ack timeout.
+    # Create-specific on purpose: MAM_INJECT_ACK_GRACE_S is the delegate-job
+    # wrapper's knob and its own tests assert on the value they pass.
+    monkeypatch.setenv("MAM_ONBOARD_ACK_S", "3")
     monkeypatch.delenv("HERDR_SESSION_NAME", raising=False)
     monkeypatch.delenv("HERDR_SERVER_NAME", raising=False)
     monkeypatch.delenv("HERDR_WORKSPACE_ID", raising=False)