feat(telemetry): ISO-8601 last_successful_submission on /api/v1/status

[erkancamli]

Closes #27

What

/api/v1/status now reports last_successful_submission as an ISO-8601 UTC timestamp (null before the first accepted submission), as requested in #27, and the field is documented.

The underlying tracking already existed: ValidatorPool stamps last_successful_submission = time.time() on every accepted submit and the controller snapshot carries it through. The endpoint just surfaced the raw float, and none of the liveness fields were in docs/rest-api.md.

Changes

• substrate/telemetry_process.py
  • new _epoch_to_iso() helper: epoch seconds → datetime.fromtimestamp(ts, tz=timezone.utc).isoformat(); None, non-numeric, NaN or out-of-range values map to null so a corrupt snapshot value never breaks the whole status response.
  • last_successful_submission is now the ISO string.
  • the raw value is kept alongside as last_successful_submission_epoch for consumers that compute staleness arithmetically (I checked dashboard.quip.network, nodes.quip.network and check.quip.network; none of them read the field yet, so this is the moment to switch the format without breaking anyone).
• docs/rest-api.md: documents is_mining, last_successful_submission, last_successful_submission_epoch, consecutive_submit_failures and runtime_incompatible with an example payload, so operators know how to read a "mining but not landing" node.
• tests/test_telemetry_process.py
  • test_epoch_to_iso_renders_utc_or_none: helper edge cases.
  • test_telemetry_status_reports_last_successful_submission_as_iso: spins up the telemetry process against a snapshot file and checks ISO + epoch, then rewrites the snapshot without the field and checks both are null.

Example

{
  "is_mining": true,
  "last_successful_submission": "2026-09-07T18:42:11.503219+00:00",
  "last_successful_submission_epoch": 1788806531.503219,
  "consecutive_submit_failures": 0,
  "runtime_incompatible": null
}

Acceptance criteria from #27

• ISO timestamp in the status response, null before the first accepted submission: yes.
• Updated only on accepted submissions, not mined-but-unsubmitted solutions: unchanged, the stamp is set in ValidatorPool right after confirm_success() on the submit path only.

Testing

python -m pytest tests/test_telemetry_process.py (7 passed) and the full set of test files that touch the status endpoint or the pool (275 passed, 2 skipped). ruff check clean on the touched files.

[erkancamli]

Closing this: it patches files that no longer exist on main.

88d6814 ("chore(cutover): delete v0.2 Python monolith; miners+chain are Rust now") removed substrate/telemetry_process.py, tests/test_telemetry_process.py and docs/rest-api.md. Git reports all three as deleted-by-main rather than as a textual conflict, so there is nothing left to rebase onto and reworking this branch in place would not make sense.

The request behind it is still unmet in the Rust coordinator, so I have left the specifics on #27 rather than keeping a stale PR open here.