fix(core-eslint): fail loudly on unparseable manifest in wiring gate

usecase-must-be-wired returned {} when the manifest parsed to null,
silently disabling the error-level gate when the manifest existed but
could not be read. It now reports unparseableManifest on Program in
that case; a genuinely missing manifest stays a no-op (that is
feature-must-have-manifest's job).

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

packages/core-eslint/rules/usecase-must-be-wired.test.js

@@ -153,6 +153,35 @@ describe("usecase-must-be-wired", () => {
     });
   });
 
+  it("reports unparseableManifest when the manifest exists but cannot be parsed", () => {
+    const { repoRoot, binderFile } = makeFixture({
+      manifestUseCases: {},
+      binderBody: `export function bindProductionDemo(ctx) {}`,
+    });
+    // Overwrite the manifest with a shape the AST walker cannot read
+    // (no defineFeature call) — the gate must fail loudly, not no-op.
+    fs.writeFileSync(
+      path.join(repoRoot, "packages", "demo", "src", "feature.manifest.ts"),
+      `export const demoManifest = { name: "demo" };`,
+    );
+    tester.run("usecase-must-be-wired", rule, {
+      valid: [],
+      invalid: [
+        {
+          filename: binderFile,
+          code: fs.readFileSync(binderFile, "utf8"),
+          options: [{ repoRoot }],
+          errors: [
+            {
+              messageId: "unparseableManifest",
+              data: { feature: "demo" },
+            },
+          ],
+        },
+      ],
+    });
+  });
+
   it("is a no-op when the feature manifest declares no use cases", () => {
     const { repoRoot, binderFile } = makeFixture({
       manifestUseCases: {},