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/test_issue23_24_startup_path.py

@@ -539,19 +539,23 @@ def test_s7c_delivery_succeeds_when_the_registry_left_pending(mam_sandbox):
     assert "DELIVERED" in res.stdout, res.stdout + res.stderr
 
 
-def test_s7d_no_started_within_t_is_a_delivery_failure(mam_sandbox):
-    """S7d: fail closed, and say so on the job."""
+def test_s7d_no_started_marks_the_job_but_keeps_the_session(mam_sandbox):
+    """S7d: the job failed, the session did not. The handshake is marked
+    `error` and warned about loudly, but a live agent is not killed over a
+    slow onboarding - the same rule this script already applies one step
+    earlier to a TUI that never signalled ready."""
     res, published = _run_delivery(mam_sandbox, 0)
-    assert res.returncode == 1, res.stdout + res.stderr
-    assert "DELIVERED" not in res.stdout
+    assert res.returncode == 0, res.stdout + res.stderr
     assert published == ["error"], published
+    assert "did not acknowledge the onboarding prompt" in res.stderr
+    assert "preserved" in res.stderr
 
 
 def test_s7e_a_started_from_another_dispatch_is_not_evidence(mam_sandbox):
     """S7e: a loop job keeps one events.log across attempts, so only a started
     carrying THIS dispatch token counts."""
-    res, _ = _run_delivery(mam_sandbox, 0, started_token="tok-OTHER")
-    assert res.returncode == 1, res.stdout + res.stderr
+    res, published = _run_delivery(mam_sandbox, 0, started_token="tok-OTHER")
+    assert published == ["error"], published
 
 
 def test_s8_rc4_is_a_warning_and_the_started_wait_decides(mam_sandbox):
@@ -564,8 +568,8 @@ def test_s8_rc4_is_a_warning_and_the_started_wait_decides(mam_sandbox):
     assert published == [], published
 
     res, published = _run_delivery(mam_sandbox, 4)
-    assert res.returncode == 1, res.stdout + res.stderr
     assert published == ["error"], published
+    assert "did not acknowledge the onboarding prompt" in res.stderr
 
 
 @pytest.mark.parametrize("rc", [1, 2, 3])