feat(unic-archon-dlc): a controls node in /build writes inert or can-fail per check into evidence.json #489

What

After verification, a node that runs each mechanism check's positive control against the run's own tree in a scratch worktree, records whether the control made the check fail, and writes controls: {<check>: inert | can-fail} into evidence.json. A check with no control, or whose control does not make it fail, is inert, never a pass.

Why

Run 3 ran the four controls for 43021–43024 by hand in a session, one at a time, after the build; 43024 needed three attempts because of the documented ordering (snapshot first, then 43023, then 43024). A hand ritual rots. The register's F5 § 1 already says a mechanism can read green by construction; this is the node that proves, per run, that it did not. Pairs with the Consumer Task that puts each control's design beside its check in checks/README.md (the node reads them from there).

Evidence

• Findings register, § "G. What run 3 taught about the instrument", row G18: 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 record § the four positive controls; register § G row G18)
• Dispatch record: #457 from comment 5698289748 down

Not decided

• Whether the node reads controls from checks/README.md (prose) or from a controls/ directory of scripts.
• Whether inert fails evidence_policy or only reports.
• Which of declaresInteractive's four branches (tabIndex, a[href], role="button", onClick) each need their own control.

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