fix(eslint): preserve TypeScript core-rule replacements

src/eslint/base.js

@@ -1,7 +1,7 @@
 /**
  * Public preset: base — framework-agnostic full stack.
  *
- * ignores + typescript + quality + testing, then prettier last. For plain TS
+ * ignores + quality + typescript + testing, then prettier last. For plain TS
  * libraries and Node packages with no Vue and no Workers runtime.
  *
  * Compose concerns directly instead if you want finer control:

src/eslint/core.js

@@ -1,5 +1,5 @@
 /**
- * Internal: the framework-agnostic core = ignores + typescript + quality +
+ * Internal: the framework-agnostic core = ignores + quality + typescript +
  * testing + tooling relaxations. NOT exported directly and deliberately does
  * NOT end with prettier — each public preset appends prettier last (after any
  * framework layer) so no formatting rules survive.
@@ -12,8 +12,10 @@ import { TOOLING_FILES } from "./globs.js";
 
 export default [
   ...ignores,
-  ...typescript,
   ...quality,
+  // TypeScript must follow the JavaScript quality layer so its extension rules
+  // can disable overlapping core rules such as no-undef and no-unused-vars.
+  ...typescript,
   ...testing,
   {
     files: TOOLING_FILES,

test/typescript-core-rule-replacements.test.mjs

@@ -0,0 +1,30 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+
+import { ESLint } from "eslint";
+
+import nodePreset from "../src/eslint/node.js";
+
+const eslint = new ESLint({
+  cwd: process.cwd(),
+  overrideConfig: nodePreset,
+  overrideConfigFile: true,
+});
+
+const severity = (rule) => rule?.[0] ?? 0;
+
+test("TypeScript extension rules replace overlapping core rules", async () => {
+  const config = await eslint.calculateConfigForFile("fixture.ts");
+
+  assert.equal(severity(config.rules["no-undef"]), 0);
+  assert.equal(severity(config.rules["no-unused-vars"]), 0);
+  assert.equal(severity(config.rules["@typescript-eslint/no-unused-vars"]), 2);
+});
+
+test("plain JavaScript keeps equivalent correctness coverage", async () => {
+  const config = await eslint.calculateConfigForFile("fixture.js");
+
+  assert.equal(severity(config.rules["no-undef"]), 2);
+  assert.equal(severity(config.rules["no-unused-vars"]), 0);
+  assert.equal(severity(config.rules["@typescript-eslint/no-unused-vars"]), 2);
+});