Read a sibling the checker does not place beside mesh-delivery from its captured copy, said (issue 1585)

The judge's tests moved from mesh-sdk, where mesh-host was beside them; the checker places only mesh-sdk and the
catalogue beside mesh-delivery (besideRules), so the node-engine's path rules failed as not beside. A sibling the run
holds beside is read there; one it does not is read from testdata/beside and the log says which; only a sibling
with neither fails.

Claude-Session: https://claude.ai/code/session_01NcbgfJ9Gum47zkFKWRaovL

modules/mesh-delivery-indexer/internal/beside/beside.go

@@ -54,18 +54,24 @@ const CapturedSuffix = ".captured"
 // says which in the test's log.
 func Dir(t testing.TB, repository string) string {
 	t.Helper()
-	if root := os.Getenv(Env); root != "" {
+	root := os.Getenv(Env)
+	if root != "" {
 		dir := filepath.Join(root, repository)
-		if _, err := os.Stat(dir); err != nil {
+		if _, err := os.Stat(dir); err == nil {
-			t.Fatalf("%s is not beside this check in %s=%s, so its agreement with this repository cannot be "+
+			t.Logf("judged against %s as cloned beside this check", dir)
-				"judged here: %v", repository, Env, root, err)
+			return dir
 		}
-		t.Logf("judged against %s as cloned beside this check", dir)
-		return dir
 	}
+	// Not beside this run: the checker places beside mesh-delivery only what its besideRules name for it (mesh-sdk and
+	// the catalogue, issue 1585), so a sibling it does not place (mesh-host) is read from the captured copy, said, and a
+	// check is never skipped. Only a sibling with neither fails.
 	from := filepath.Join(Captured(), repository)
 	if _, err := os.Stat(from); err != nil {
-		t.Fatalf("no captured copy of %s at %s: %v", repository, from, err)
+		t.Fatalf("%s is neither beside this check (%s=%q) nor captured at %s: %v", repository, Env, root, from, err)
+	}
+	if root != "" {
+		t.Logf("%s is not beside this check in %s=%s (the checker places it beside no mesh-delivery check): read from "+
+			"its captured copy", repository, Env, root)
 	}
 	dir, err := layOut(repository, from)
 	if err != nil {