A module answers the word the mesh asks: prepare

The runtime gains `prepare`, which brings this module's state to the shape this version needs and
exits (novox/hq ADR 0135). The entrypoints come from MESH_PREPARE, which a module's own image names
beside the entrypoints it already lists there — the module knows which of its files prepares its
state and nothing else could. No broker is connected: preparation runs before the version that would
use it. An empty list fails rather than passing quietly, because the mesh asks this only of a module
whose manifest says it prepares something, and exiting 0 would let that version serve against a
state nobody shaped.

test/patient-connect.test.ts

@@ -1,3 +1,4 @@
+import { spawn } from "node:child_process";
 import { test } from "node:test";
 import assert from "node:assert/strict";
 import { fatalBrokerReason, PinMismatchError } from "../src/broker-nats.ts";
@@ -41,3 +42,21 @@ test("a non-Error value does not crash the classifier", () => {
   assert.equal(fatalBrokerReason("just a string"), null);
   assert.equal(fatalBrokerReason(undefined), null);
 });
+
+// **A module asked to prepare its state and naming nothing is a failure, not a no-op** (novox/hq
+// ADR 0135). The mesh asks this only of a module whose manifest says it prepares something, so an
+// image that names nothing was built wrong, and exiting 0 would let that version serve against a
+// state nobody shaped.
+test("preparing with nothing named fails rather than passing quietly", async () => {
+  const runtime = new URL("../dist/main.js", import.meta.url).pathname;
+  const ran = await new Promise<{ code: number | null; said: string }>((resolve) => {
+    const child = spawn(process.execPath, [runtime, "prepare"], {
+      env: { ...process.env, MESH_PREPARE: "" },
+    });
+    let said = "";
+    child.stderr.on("data", (chunk) => (said += String(chunk)));
+    child.on("close", (code) => resolve({ code, said }));
+  });
+  assert.notEqual(ran.code, 0, "a module that prepares nothing exited 0, so its version would serve");
+  assert.match(ran.said, /MESH_PREPARE/);
+});