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/plugin.js

@@ -11,6 +11,8 @@ import atomicTierImportDirection from "./rules/atomic-tier-import-direction.js";
 import piiDeclarationMustBeComplete from "./rules/pii-declaration-must-be-complete.js";
 import noUndeclaredConsentCheck from "./rules/no-undeclared-consent-check.js";
 import noUndeclaredRateLimit from "./rules/no-undeclared-rate-limit.js";
+import entityMustHaveTest from "./rules/entity-must-have-test.js";
+import noRelativeParentImportInTests from "./rules/no-relative-parent-import-in-tests.js";
 
 /**
  * The `@repo/core-eslint` conformance plugin. Aggregates custom rules that
@@ -26,7 +28,7 @@ import noUndeclaredRateLimit from "./rules/no-undeclared-rate-limit.js";
  *   ];
  */
 const plugin = {
-  meta: { name: "conformance", version: "0.3.0" },
+  meta: { name: "conformance", version: "0.4.0" },
   rules: {
     "feature-must-have-manifest": featureMustHaveManifest,
     "usecase-must-have-test-file": usecaseMustHaveTestFile,
@@ -41,6 +43,8 @@ const plugin = {
     "pii-declaration-must-be-complete": piiDeclarationMustBeComplete,
     "no-undeclared-consent-check": noUndeclaredConsentCheck,
     "no-undeclared-rate-limit": noUndeclaredRateLimit,
+    "entity-must-have-test": entityMustHaveTest,
+    "no-relative-parent-import-in-tests": noRelativeParentImportInTests,
   },
 };