feat(core-eslint): anchor for events rules splice

Add // <gen:events-rules> anchor to base.js near the E1 + J
no-restricted-syntax blocks, and assert it in anchors.test.js.
After core-events removal the anchor remains as the splice point
for pnpm turbo gen core-package events.

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

packages/core-eslint/anchors.test.js

@@ -20,6 +20,11 @@ describe("// <gen:*> anchor presence in core-eslint/base.js", () => {
     expect(baseSource).toContain("// <gen:realtime-rules-imports>");
     expect(baseSource).toContain("// <gen:realtime-rules>");
   });
+
+  it("base.js contains events-rules anchor", () => {
+    const baseSource = readFileSync(join(REPO_ROOT, "packages/core-eslint/base.js"), "utf8");
+    expect(baseSource).toContain("// <gen:events-rules>");
+  });
 });
 
 describe("// <gen:*> anchor presence in feature packages", () => {