fix(issue-33): subscriber exit codes are named on both sides; wait keeps a spent budget at rc 2; G-8 is deterministic

- job_subscriber.py returns only named codes (RC_COMPLETED 0, RC_ERROR 1,
  RC_NO_EVENT 2, RC_BROKER_UNAVAILABLE 3, RC_WALL_CLOCK 4). The wrapper
  mirrors them as SUB_RC_* and compares subscriber codes only by name; a test
  keeps the mirror equal to the Python constants and forbids numeric
  comparisons of $sub_rc/$sub_exit and numeric `return` in the subscriber.
- `delegate-job wait` passed the subscriber's code straight through, so a
  spent budget would have reached its callers as 4; it is 2 again (B7 fails
  without the mapping).
- tier1 G-8 gave both clocks 0.5 s and raced; the wall clock now runs out
  first by construction (idle 30 s) and the test asserts RC_WALL_CLOCK.
  Other subscriber rc asserts use the names.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_issue18_liveness_contract.py

@@ -1030,7 +1030,7 @@ def test_a_replayed_retained_state_does_not_keep_a_silent_job_alive(tmp_path, mo
                   "--timeout", "20"])
     elapsed = time.monotonic() - started
     fake.stopped.set()
-    assert rc == 2
+    assert rc == js.RC_NO_EVENT
     assert elapsed < 8, f"the replayed state kept the silent job alive for {elapsed:.1f}s"