feat(core): add 8 AGENTS.md files (package, layer, domain levels)

packages/core/AGENTS.md

@@ -0,0 +1,48 @@
+# @repo/core — Clean Architecture Core
+
+Business logic package. All use cases, entities, interfaces, and DI live here.
+
+## Layers (dependencies point inward only)
+
+```
+entities/          → NOTHING (innermost, zero deps)
+application/       → entities/ only
+interface-adapters/→ application/, entities/
+infrastructure/    → application/, entities/, @repo/cms-client, external libs
+di/                → all internal layers
+```
+
+## Import Rules
+
+| Layer | Can import from | NEVER import from |
+|---|---|---|
+| entities/ | NOTHING | Everything else |
+| application/ | entities/ only | infrastructure/, interface-adapters/ |
+| interface-adapters/ | application/, entities/ | infrastructure/ |
+| infrastructure/ | application/, entities/, @repo/cms-client | interface-adapters/, apps/* |
+| di/ | All internal layers | apps/* |
+
+## DI Resolution Table
+
+| Symbol | Interface | Production | Mock |
+|---|---|---|---|
+| IUsersRepository | IUsersRepository | PayloadUsersRepository (Plan 3) | MockUsersRepository |
+| IArticlesRepository | IArticlesRepository | PayloadArticlesRepository (Plan 3) | MockArticlesRepository |
+| IAuthenticationService | IAuthenticationService | BetterAuthService (future) | MockAuthenticationService |
+| ITelemetryService | ITelemetryService | OTelSentryService (future) | MockTelemetryService |
+
+## Naming Conventions
+
+- Models: `{name}.ts` with Zod schema + type export
+- Errors: `{domain}.ts` with Error subclasses
+- Interfaces: `{name}.repository.interface.ts` or `{name}.service.interface.ts`
+- Use cases: `{verb}-{noun}.use-case.ts`
+- Controllers: `{noun}.controller.ts`
+- Infra: `{provider}-{name}.repository.ts` or `mock-{name}.repository.ts`
+- DI modules: `{domain}.module.ts`
+
+## Running Tests
+
+```bash
+cd packages/core && pnpm vitest run
+```