mesh-controller's try asked build-agent, which leaves the checking at R4e. A try is now a key in the checker's state
tries: the checker judges the head merged onto its trunk as it judges a pull request's head, through the same
judge, places and holds, writes its end in the key and owes the forge nothing (no status, no preview, no verdict).
One try per head, at most four at once; hq and a repository whose trunk the gate does not name are refused with
"no level of <repo> is checked by the checker".
The gate decides on mesh/check alone and matches an Approve's members by the heads hash over lowercase repositories
and heads. A success judged on an old trunk stood on the forge while the next check waited for a place or a delivery,
and a candidate whose repository the forge named in capitals carried a hash the gate never finds. A check that ends
after its trunk moved now owes pending, not its verdict.