bug(unic-archon-dlc, upstream: Archon): a loop node reports its last iteration's duration as the node's #493

Observed

Run 3 build c283e296, run-build (the slice loop): console [run-build] Completed (1m6s), event row duration_ms: 65697. The commits it produced span 18:58:45 to 19:22:31, about 24 minutes. The non-loop nodes report correctly (implement-review-precheck 214548 ms against 3m35s observed).

Why it matters

Anyone reading the event row for cost or elapsed time reads the fourth slice only. The register's run-2 cost proxy is already marked not comparable for another reason; this makes any node-level timing of the build unusable until fixed.

Evidence

• Findings register, § "G. What run 3 taught about the instrument", row G10: https://github.com/unic/unic-agents-plugins/blob/bcf688a/docs/research/2026-08-31-dlc-run-2-findings.md
• Run record and harvested artefacts: ~/Desktop/run3-parked/ on the maintainer's machine (run-c283e296-events-1933-final.json (node_completed for run-build), git log --format=%ad 7f8fedd..08e2523)
• Dispatch record: #457 from comment 5698289748 down

Not decided

• Upstream: whether the loop node should sum iterations or emit one event per iteration.

Filed 2026-09-17 by wayfinder-orchestrator-10 from run 3's measurements. needs-specs: grill before dispatch.