Check a delivery group's member beside its siblings' merges, judged by the group's controller (issue 867, ADR 0382)

A mesh-host change and a mesh-controller change that need each other could not both pass their own checks: each read the other at its base. The check now asks mesh-delivery for the group's open siblings into a base of the same name, reads each at its head merged onto its base, builds the judge from a controller sibling's merge in the isolated judge environment keyed on its inputs, and names the siblings in the verdict. With no answer from mesh-delivery the verdict says it could not learn them; a pull request with no sibling is checked as before. TestReplay867 replays the failure.

Co-Authored-By: Claude <noreply@anthropic.com>

cmd/mesh-builder/release_test.go

@@ -3,6 +3,7 @@ package main
 import (
 	"testing"
 
+	"github.com/novox/mesh-controller/internal/builder"
 	"github.com/novox/mesh-controller/internal/link"
 )
 
@@ -25,3 +26,21 @@ func TestTheBuildSeatHandsTheCheckItsReleaseBranch(t *testing.T) {
 		t.Fatalf("with no judge cache declared, %q is used", got)
 	}
 }
+
+// The siblings a check is asked to read reach the build seat's spec and, as read, the outcome (novox/hq ADR 0382).
+func TestTheSiblingsAnAskNamesReachTheSpecAndTheOutcome(t *testing.T) {
+	spec := checkSpecOf(link.BuildRequest{Check: &link.CheckRequest{Owner: "novox", Repo: "mesh-host", Base: "main",
+		Siblings:        []link.CheckSibling{{Repository: "novox/mesh-controller", Number: 346, Head: "a", Base: "main", Dir: "mesh-controller"}},
+		SiblingsUnknown: "why"}})
+	if len(spec.Siblings) != 1 || spec.Siblings[0] != (builder.Sibling{Repository: "novox/mesh-controller", Number: 346,
+		Head: "a", Base: "main", Dir: "mesh-controller"}) || spec.SiblingsUnknown != "why" {
+		t.Fatalf("the spec reads %+v", spec)
+	}
+	out := siblingsOut([]builder.JudgedSibling{{Repository: "novox/mesh-controller", Number: 346, Head: "a", Base: "main", BaseCommit: "b"}})
+	if len(out) != 1 || out[0].BaseCommit != "b" || out[0].Number != 346 {
+		t.Fatalf("the outcome reads %+v", out)
+	}
+	if plain := checkSpecOf(link.BuildRequest{Check: &link.CheckRequest{Owner: "o", Repo: "r"}}); plain.Siblings != nil {
+		t.Fatalf("a request that names none has siblings %+v", plain.Siblings)
+	}
+}