feat(core-eslint): feature-must-have-manifest rule

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/core-eslint/rules/feature-must-have-manifest.js

@@ -0,0 +1,49 @@
+import fs from "node:fs";
+import { manifestPathForFeature, featureRootForFile } from "./_manifest-source.js";
+
+/** @type {import("eslint").Rule.RuleModule} */
+export default {
+  meta: {
+    type: "problem",
+    docs: {
+      description:
+        "Every feature with use-case files must declare a feature.manifest.ts at its src/ root.",
+    },
+    schema: [
+      {
+        type: "object",
+        properties: {
+          repoRoot: { type: "string" },
+        },
+        additionalProperties: false,
+      },
+    ],
+    messages: {
+      missingManifest:
+        "Feature {{feature}} has use cases but no feature.manifest.ts. Run `pnpm turbo gen feature {{feature}}` or scaffold the manifest manually at {{expected}}.",
+    },
+  },
+  create(context) {
+    const opts = context.options[0] ?? {};
+    const repoRoot = opts.repoRoot ?? context.cwd ?? process.cwd();
+    return {
+      Program(node) {
+        const filename = context.filename;
+        const featureRoot = featureRootForFile(filename, repoRoot);
+        if (!featureRoot) return;
+        // Only check use-case files
+        if (!filename.includes("/application/use-cases/") || !filename.endsWith(".use-case.ts")) {
+          return;
+        }
+        const manifestPath = manifestPathForFeature(featureRoot);
+        if (fs.existsSync(manifestPath)) return;
+        const featureName = featureRoot.split("/").pop();
+        context.report({
+          node,
+          messageId: "missingManifest",
+          data: { feature: featureName, expected: manifestPath },
+        });
+      },
+    };
+  },
+};