test(issue-14): widen the wall-clock close margin under suite load

The close landed 8-9 s past the 20 s deadline in three full-suite runs on
this host (all passed alone); the pinned defect closed at ~2 x TIMEOUT,
so a 15 s margin keeps the test meaningful.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VCgu9Fa9iT7TbJUSzdq4Ff

tests/test_issue14_delivery_ack.py

@@ -510,7 +510,10 @@ def test_wrapper_idle_grace_never_outlives_the_wall_clock(tmp_path):
     import calendar
     closed_at = calendar.timegm(time.strptime(job_data["updated_at"], "%Y-%m-%dT%H:%M:%SZ"))
     close_delay = closed_at - started
-    assert close_delay <= timeout_s + 8, f"idle grace outlived --timeout {timeout_s}s: closed after {close_delay:.0f}s\n{stderr}"
+    # Under full-suite load the wrapper's final poll, close and registry write
+    # have landed 8-9 s past the deadline (three full runs); the defect this
+    # pins was a close at ~2 x TIMEOUT, so a 15 s margin still separates them.
+    assert close_delay <= timeout_s + 15, f"idle grace outlived --timeout {timeout_s}s: closed after {close_delay:.0f}s\n{stderr}"
 
 
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