fix(conformance): fail the CI gate on unparseable manifests

parseManifestUseCases returning null for a manifest that exists made
the cross-feature gate silently skip that feature. findUnparseableManifests
now runs before the empty-graph early exit (an unparseable manifest
contributes zero events and would otherwise pass as nothing-to-check)
and any hit fails the run. Reader-closure from the downstream fork is
not ported: this tree has no reads: manifests or ./reader exports yet.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/conformance.test.mjs

@@ -2,7 +2,12 @@ import { describe, it, expect } from "vitest";
 import path from "node:path";
 import os from "node:os";
 import fs from "node:fs";
-import { findAllManifests, buildEventGraph, findOrphanConsumers } from "./conformance.mjs";
+import {
+  findAllManifests,
+  findUnparseableManifests,
+  buildEventGraph,
+  findOrphanConsumers,
+} from "./conformance.mjs";
 
 function makeRepo(features) {
   const root = fs.mkdtempSync(path.join(os.tmpdir(), "conformance-"));
@@ -10,8 +15,9 @@ function makeRepo(features) {
     const dir = path.join(root, "packages", name, "src");
     fs.mkdirSync(dir, { recursive: true });
     const useCasesStr = Object.entries(useCases)
-      .map(([ucName, uc]) =>
-        `    ${ucName}: { mutates: ${uc.mutates ?? false}, audits: [], publishes: [${(uc.publishes ?? []).map((p) => `"${p}"`).join(", ")}], consumes: [${(uc.consumes ?? []).map((c) => `"${c}"`).join(", ")}] },`,
+      .map(
+        ([ucName, uc]) =>
+          `    ${ucName}: { mutates: ${uc.mutates ?? false}, audits: [], publishes: [${(uc.publishes ?? []).map((p) => `"${p}"`).join(", ")}], consumes: [${(uc.consumes ?? []).map((c) => `"${c}"`).join(", ")}] },`,
       )
       .join("\n");
     fs.writeFileSync(
@@ -43,11 +49,34 @@ describe("conformance script", () => {
 
     it("skips packages without a manifest", () => {
       const root = fs.mkdtempSync(path.join(os.tmpdir(), "conformance-empty-"));
-      fs.mkdirSync(path.join(root, "packages", "no-manifest", "src"), { recursive: true });
+      fs.mkdirSync(path.join(root, "packages", "no-manifest", "src"), {
+        recursive: true,
+      });
       expect(findAllManifests(root)).toEqual([]);
     });
   });
 
+  describe("findUnparseableManifests", () => {
+    it("flags a manifest the AST parser cannot read", () => {
+      const root = makeRepo({ auth: { signIn: {} } });
+      const brokenDir = path.join(root, "packages", "broken", "src");
+      fs.mkdirSync(brokenDir, { recursive: true });
+      // No defineFeature call — parseManifestUseCases returns null.
+      fs.writeFileSync(
+        path.join(brokenDir, "feature.manifest.ts"),
+        `export const brokenManifest = { name: "broken" };`,
+      );
+      const manifests = findAllManifests(root);
+      const unparseable = findUnparseableManifests(manifests);
+      expect(unparseable.map((m) => m.feature)).toEqual(["broken"]);
+    });
+
+    it("returns [] when every manifest parses", () => {
+      const root = makeRepo({ auth: { signIn: {} } });
+      expect(findUnparseableManifests(findAllManifests(root))).toEqual([]);
+    });
+  });
+
   describe("buildEventGraph + findOrphanConsumers", () => {
     it("finds zero orphans when consumers and publishers line up", () => {
       const root = makeRepo({
@@ -68,7 +97,9 @@ describe("conformance script", () => {
       const orphans = findOrphanConsumers(graph);
       expect(orphans).toHaveLength(1);
       expect(orphans[0].event).toBe("auth.signed-up");
-      expect(orphans[0].consumers).toEqual([{ feature: "marketing", useCase: "onAuthSignedUp" }]);
+      expect(orphans[0].consumers).toEqual([
+        { feature: "marketing", useCase: "onAuthSignedUp" },
+      ]);
     });
 
     it("treats publish-only events as fine (no consumers is not an orphan)", () => {