What review found in the port machinery, fixed

Three faults, one file split. All from reading, all verified to bite.

Unassign now releases the module's ports. ReleasePorts existed, said
"for when it is unassigned" in its own comment, and was called by
nothing — so a fixed port stayed claimed in the name of a module that
was gone, and the next module needing it was refused by a ghost.
Kept-once-chosen is a promise about a module that is still here.

MachineSide reads addressed mappings. "127.0.0.1:8080:80" was split at
the first colon, "127.0.0.1" failed to parse as a port, and the mapping
was silently skipped — putting the filter back on the declared port,
the exact fault the function was written to end. The machine side is
the second-from-last part, which is the reading the host already
applies, and the substrate bundle writes that shape today.

An allocation race answers in the mesh's words. Two concurrent picks of
the same port used to surface as a Postgres constraint violation,
verbatim. The table has two keys, so the collision is one of two facts:
the racer was this same assignment — then its answer is the answer,
kept-once-chosen does not care who chose — or another module took the
machine port, and an unfixed pick is simply made again against the
moved free list. A fixed port that lost the race is refused by name.
Told apart by re-reading the row, not by the constraint's name, so this
does not couple to the migration's spelling.

And the artifact-store cycle tests moved to bootstrap_cycle_test.go;
machineside_test.go had quietly become three subjects.

internal/catalogue/bootstrap_cycle_test.go

@@ -0,0 +1,71 @@
+package catalogue
+
+import (
+	"strings"
+	"testing"
+)
+
+// The module that provides the artifact store may not be delivered through it.
+//
+// Building publishes to the store and the builder will not start without one, so a module that
+// provides the store and also builds something asks the mesh to put an artifact into the thing
+// that artifact is needed to create. On a mesh new enough to have no registry, that is a build
+// that never returns (novox/hq 04-ISSUES/029).
+func TestTheArtifactStoreCannotBeDeliveredThroughItself(t *testing.T) {
+	_, err := ParseManifest([]byte(`{"module":"registry","version":"1",` +
+		`"provides":[{"name":"artifact-store","scope":"mesh"}],` +
+		`"build":{"artifacts":[{"name":"registry","kind":"upstream","from":"registry:2"}]},` +
+		`"resources":[{"id":"store","type":"container","name":"mesh-registry",` +
+		`"artifact":"registry","ports":["5000:5000"]}]}`))
+	if err == nil {
+		t.Fatal("a registry module that builds its own image was accepted; the build has " +
+			"nowhere to publish until the module it belongs to is already running")
+	}
+	if !strings.Contains(err.Error(), "artifact-store") {
+		t.Fatalf("refused without naming the provision the cycle turns on: %v", err)
+	}
+}
+
+// Naming the image directly is the way out, and must stay accepted.
+func TestAnArtifactStoreThatNamesItsImageIsAccepted(t *testing.T) {
+	_, err := ParseManifest([]byte(`{"module":"registry","version":"1",` +
+		`"provides":[{"name":"artifact-store","scope":"mesh"}],` +
+		`"resources":[{"id":"store","type":"container","name":"mesh-registry",` +
+		`"image":"registry@sha256:` +
+		`266f282fabd7cd3df053ee7c658c77b42380d1a2f0d8e5a1c0d7a6d5b5c4a3b2",` +
+		`"ports":["5000:5000"]}]}`))
+	if err != nil {
+		t.Fatalf("the one way an artifact store can be delivered was refused: %v", err)
+	}
+}
+
+// And an ordinary module still builds whatever it likes.
+func TestAModuleThatDoesNotProvideTheStoreStillBuilds(t *testing.T) {
+	_, err := ParseManifest([]byte(`{"module":"forge","version":"1",` +
+		`"build":{"artifacts":[{"name":"forge","kind":"upstream","from":"gitea/gitea:1.22"}]},` +
+		`"resources":[{"id":"run","type":"container","name":"forge","artifact":"forge"}]}`))
+	if err != nil {
+		t.Fatalf("an ordinary module was caught by a rule about the artifact store: %v", err)
+	}
+}
+
+// A mapping that names an address still names the port, and the machine side is still the middle.
+//
+// The substrate bundle writes "127.0.0.1:5432:5432" today, so the shape is not hypothetical.
+// Found in review: the first cut split on the first colon, read "127.0.0.1" as the machine port,
+// failed to parse it, and silently skipped the mapping — which put the filter back on the
+// declared port, the exact fault MachineSide was written to end.
+func TestAnAddressedMappingStillNamesThePort(t *testing.T) {
+	m := Manifest{Module: "store", Resources: []map[string]any{
+		{"type": "container", "id": "server", "ports": []any{"127.0.0.1:8080:80"}},
+	}}
+	for _, named := range []int{8080, 80} {
+		at, mayAssign := m.MachineSide(named)
+		if mayAssign {
+			t.Fatalf("%d was reassigned though the manifest published it explicitly", named)
+		}
+		if at != 8080 {
+			t.Fatalf("naming %d gave %d; the machine side of 127.0.0.1:8080:80 is 8080", named, at)
+		}
+	}
+}