chore: officially migrate to submodule (#4502)

* remove apps/core and apps/fern

* fix precommit

* add submodule updates in workflows

* submodule

* remove core tests

* update core revision

* Add submodules: true to all GitHub workflows

- Ensure all workflows can access git submodules
- Add submodules support to deployment, test, and CI workflows
- Fix YAML syntax issues in workflow files

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* remove core-lint

* upgrade core with latest main of oss

---------

Co-authored-by: Claude <noreply@anthropic.com>

dev-compose.yaml

@@ -1,47 +0,0 @@
-services:
-  letta_db:
-    image: ankane/pgvector:v0.5.1
-    networks:
-      default:
-        aliases:
-          - pgvector_db
-          - letta-db
-    environment:
-      - POSTGRES_USER=${LETTA_PG_USER:-letta}
-      - POSTGRES_PASSWORD=${LETTA_PG_PASSWORD:-letta}
-      - POSTGRES_DB=${LETTA_PG_DB:-letta}
-    volumes:
-      - ./.persist/pgdata-test:/var/lib/postgresql/data
-      - ./init.sql:/docker-entrypoint-initdb.d/init.sql
-    ports:
-      - "5432:5432"
-  letta_server:
-    image: letta/letta:latest
-    hostname: letta
-    build:
-      context: .
-      dockerfile: Dockerfile
-      target: runtime
-    depends_on:
-      - letta_db
-    ports:
-      - "8083:8083"
-      - "8283:8283"
-    environment:
-      - LETTA_PG_DB=${LETTA_PG_DB:-letta}
-      - LETTA_PG_USER=${LETTA_PG_USER:-letta}
-      - LETTA_PG_PASSWORD=${LETTA_PG_PASSWORD:-letta}
-      - LETTA_PG_HOST=pgvector_db
-      - LETTA_PG_PORT=5432
-      - LETTA_DEBUG=True
-      - OPENAI_API_KEY=${OPENAI_API_KEY}
-      - GROQ_API_KEY=${GROQ_API_KEY}
-      - ANTHROPIC_API_KEY=${ANTHROPIC_API_KEY}
-      - OLLAMA_BASE_URL=${OLLAMA_BASE_URL}
-      - AZURE_API_KEY=${AZURE_API_KEY}
-      - AZURE_BASE_URL=${AZURE_BASE_URL}
-      - AZURE_API_VERSION=${AZURE_API_VERSION}
-      - GEMINI_API_KEY=${GEMINI_API_KEY}
-      - VLLM_API_BASE=${VLLM_API_BASE}
-      - OPENLLM_AUTH_TYPE=${OPENLLM_AUTH_TYPE}
-      - OPENLLM_API_KEY=${OPENLLM_API_KEY}