feat(core-eslint): add entity-must-have-test and no-relative-parent-import rules

Two CLAUDE.md conventions had no mechanical gate, so both drifted:
entity models shipped without sibling tests, and feature test files
imported src modules via `../` instead of the `@/` alias.

- `entity-must-have-test` — every entities/models/<x>.ts needs a sibling
  <x>.test.ts (errors and barrels excluded).
- `no-relative-parent-import-in-tests` — feature test files must import
  src via `@/`, not `../`. Scoped to feature packages; core packages are
  governed by their own generator templates.

Both register at warn level, bringing the conformance rule count to 15.

packages/core-eslint/rules/no-relative-parent-import-in-tests.test.js

@@ -0,0 +1,73 @@
+import { describe, it } from "vitest";
+import { RuleTester } from "eslint";
+import rule from "./no-relative-parent-import-in-tests.js";
+
+const tester = new RuleTester({
+  languageOptions: { ecmaVersion: "latest", sourceType: "module" },
+});
+
+const featureTest = "/repo/packages/auth/src/di/container.test.ts";
+const featureSrc = "/repo/packages/auth/src/di/container.ts";
+const coreTest = "/repo/packages/core-audit/src/di/bind-audit.test.ts";
+
+describe("no-relative-parent-import-in-tests", () => {
+  it("passes when a feature test uses the @/ alias", () => {
+    tester.run("no-relative-parent-import-in-tests", rule, {
+      valid: [
+        {
+          filename: featureTest,
+          code: `import { x } from "@/infrastructure/x";`,
+        },
+      ],
+      invalid: [],
+    });
+  });
+
+  it("passes for same-directory ./ imports", () => {
+    tester.run("no-relative-parent-import-in-tests", rule, {
+      valid: [
+        { filename: featureTest, code: `import { x } from "./container";` },
+      ],
+      invalid: [],
+    });
+  });
+
+  it("fires when a feature test imports via ../", () => {
+    tester.run("no-relative-parent-import-in-tests", rule, {
+      valid: [],
+      invalid: [
+        {
+          filename: featureTest,
+          code: `import { x } from "../infrastructure/x";`,
+          errors: [
+            {
+              messageId: "relativeParentImport",
+              data: { source: "../infrastructure/x" },
+            },
+          ],
+        },
+      ],
+    });
+  });
+
+  it("ignores ../ imports in non-test source files", () => {
+    tester.run("no-relative-parent-import-in-tests", rule, {
+      valid: [
+        {
+          filename: featureSrc,
+          code: `import { x } from "../infrastructure/x";`,
+        },
+      ],
+      invalid: [],
+    });
+  });
+
+  it("ignores core-package test files (governed by their own templates)", () => {
+    tester.run("no-relative-parent-import-in-tests", rule, {
+      valid: [
+        { filename: coreTest, code: `import { x } from "../noop-audit-log";` },
+      ],
+      invalid: [],
+    });
+  });
+});