fix(settle_epoch): exit non-zero when settlement fails

[Scottcjn]

Problem

node/settle_epoch.py is run unattended; the scheduler's only signal is the exit code. trigger_settlement() catches every exception and returns None, non-200 returns the response text, and __main__ printed the result and exited 0 in every case. An unreachable node, a malformed /epoch, or a 500 from /rewards/settle all looked like success.

Fix (1 source file + 1 test)

• main() -> int: exit 0 only when /rewards/settle returned 200 with a JSON object that does not say ok: false; otherwise exit 1 and print SETTLEMENT FAILED to stderr.
• All existing logging kept (same stdout lines). trigger_settlement()'s return contract is untouched, so tests/test_settle_epoch.py still passes unchanged.
• NODE_URL can be overridden with RC_NODE_URL (default unchanged) — used by the end-to-end test.

Regression test — tests/test_settle_epoch_exit_code.py

Unit tests for each failure shape plus an end-to-end subprocess run of the real script against a closed port.

On main (fix stashed):

FAILED test_main_exits_zero_on_successful_settlement
FAILED test_main_exits_nonzero_when_node_unreachable
FAILED test_main_exits_nonzero_on_http_error_from_settle
FAILED test_main_exits_nonzero_when_node_reports_ok_false
FAILED test_main_exits_nonzero_on_malformed_epoch_response
FAILED test_script_process_exit_code_nonzero_when_node_down
6 failed, 6 passed in 0.30s      (the 6 passes are the pre-existing tests)

With fix: 12 passed in 0.29s

Existing suite (local, Python 3.13): root pytest tests/ (CI ignores applied) — main: 4006 passed / 47 skipped / 2 xfailed; this branch: 4012 passed, same skips, 0 new failures. node/tests — main: 107–108 failed / 17 errors pre-existing (flaky between identical runs on main: one live-endpoint network test and test_sophia_elya_service.py::test_finalize_epoch_excludes_poisoned_negative_weight_rows); this branch: 108 failed / 1746 passed / 17 errors, diff vs. main by test name = only those two flaky ones. No test that passes on main fails here.

Risk before deploy

• If a cron/systemd timer wraps this script with something that alerts on non-zero exit, it will start alerting — that is the point, but expect noise on the first run if settlement is currently failing silently.
• /rewards/settle is admin-rate-limited; this script sends no admin key (pre-existing, not changed here). If it is currently 401/429-ing, this PR makes that visible.

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AI-assisted disclosure: this PR was written by Claude (Fable 5.1) working as an engineering agent for Scott / Elyan Labs, in a fresh clone, with the tests run locally as shown above. Please review as you would any contributor PR.

🤖 Generated with Claude Code

[github-actions]

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