Judge the controller's module check against the catalogue it is released with, captured at the group's catalogue head f3a57dcc, so a group that brings a word the trunk's catalogue lacks does not fail on the trunk (issue 774)

The release's fourth check failed TestModuleCheckPassesTheCatalogue with 27 problems. The checker clones the catalogue
beside a controller's tests at its trunk, even in a group holding a catalogue pull request (mesh-delivery checker
internal/check/beside.go besideFor, ADR 0484 clause 4). The release's sdk refuses an offer stating no credential form,
and the trunk's catalogue states none until the release's catalogue merges.

- Quick fix (not chosen): recapture alone, which the test never reads while MESH_CHECK_BESIDE is set.
- Chosen: the test reads the captured copy, now at the group's catalogue f3a57dcc, through beside.CapturedDir. Every other
  beside test still reads the clone. The check itself is unchanged: every rule, every manifest. Moving CAPTURED to the
  catalogue a change is released with is part of that change.

Run as the checker runs it (catalogue at main, mesh-host at main, mesh-sdk at the pin, mesh-controller's trunk
beside): the whole unit and integration suite passes, 1706 tests, 8 skipped. The test also passes with the catalogue at
f3a57dcc beside, and with nothing beside.

internal/beside/beside.go

@@ -53,6 +53,16 @@ func Dir(t testing.TB, repository string) string {
 		t.Logf("judged against %s as cloned beside this check", dir)
 		return dir
 	}
+	t.Logf("no %s beside this check: a merge check judges %s against its own clone", Env, repository)
+	return CapturedDir(t, repository)
+}
+
+// CapturedDir is the copy of the named repository captured in testdata/beside, laid out as Dir lays it out, whatever
+// MESH_CHECK_BESIDE says: for a test that judges this repository against the commit it was released with, which a
+// merge check does not clone (it clones the catalogue at its trunk even in a delivery group holding a catalogue pull
+// request, ADR 0484 clause 4).
+func CapturedDir(t testing.TB, repository string) string {
+	t.Helper()
 	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)
@@ -81,8 +91,7 @@ func Dir(t testing.TB, repository string) string {
 	if err != nil {
 		t.Fatalf("the captured copy of %s could not be laid out: %v", repository, err)
 	}
-	t.Logf("judged against the copy of %s captured in testdata/beside (see CAPTURED); a merge check "+
-		"judges it against the repository's own clone", repository)
+	t.Logf("judged against the copy of %s captured in testdata/beside (see CAPTURED)", repository)
 	return dir
 }