fix(followups): F2 - job_subscriber returns the env-file failure by name

5edf913 gave job_subscriber.main a bare `return 1`; its exit codes are
returned by name (test_issue5 test_job_subscriber_cli_contract_snapshot).
The value stays 1 - what the EnvFileError traceback exited with before -
and is RC_ERROR. The wrapper reads the same file first and exits 1 itself,
so it never starts a subscriber that would report this.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HCGpJXhSZasJLU38ksDghe

.agents/skills/lib_py/delegation/job_subscriber.py

@@ -588,7 +588,9 @@ def main(argv=None) -> int:
     args = parser.parse_args(argv)
 
     if not mqtt_common.load_env_or_report():
-        return 1
+        # rc 1, as the EnvFileError traceback exited before. The wrapper reads
+        # the same file first and exits 1 itself, so it never sees this one.
+        return RC_ERROR
     mqtt_common.setup_logging(logging.DEBUG if args.verbose else logging.WARNING)
 
     try: