Improve Codex happy path prompt snapshots (#76229)

* test: add Codex model prompt layers to snapshots

* test: keep rendered prompt snapshots raw

* test: check prompt snapshot drift in ci

* test: prefer codex model cache for prompt fixtures

* fix: exclude publishable plugin dist from core package

scripts/check-docker-e2e-boundaries.mjs

@@ -12,6 +12,9 @@ const ROOT_DIR = path.resolve(path.dirname(fileURLToPath(import.meta.url)), ".."
 const errors = [];
 const packageJson = JSON.parse(readText("package.json"));
 const packageScripts = new Set(Object.keys(packageJson.scripts ?? {}));
+// This lane proves the published Codex npm plugin against live OpenAI auth, so
+// it intentionally needs both live credentials and the package-backed image.
+const livePackageBackedLanes = new Set(["live-codex-npm-plugin"]);
 
 function readText(relativePath) {
   return fs.readFileSync(path.join(ROOT_DIR, relativePath), "utf8");
@@ -71,7 +74,7 @@ function validateLane(label, lane) {
       `${label}: Docker E2E lane '${lane.name}' has invalid image kind '${lane.e2eImageKind}'`,
     );
   }
-  if (lane.live && lane.e2eImageKind && !resources.includes("npm")) {
+  if (lane.live && lane.e2eImageKind && !livePackageBackedLanes.has(lane.name)) {
     errors.push(`${label}: live Docker E2E lane '${lane.name}' must not require a package image`);
   }
   if (!lane.live && !lane.e2eImageKind) {