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>

tests/test_tool_schema_parsing_files/all_python_complex.json

@@ -1,37 +0,0 @@
-{
-    "name": "check_order_status",
-    "description": "Check the status for an order number (integer value).",
-    "parameters": {
-      "type": "object",
-      "properties": {
-        "order_number": {
-            "type": "integer",
-            "description": "The order number to check on."
-        },
-        "customer_name": {
-            "type": "string",
-            "description": "The name of the customer who placed the order."
-        },
-        "related_tickets": {
-            "type": "array",
-            "description": "A list of ticket numbers related to the order.",
-            "items": {
-                "type": "string"
-            }
-        },
-        "related_ticket_reasons": {
-            "type": "object",
-            "description": "A dictionary of reasons for the related tickets."
-        },
-        "severity": {
-            "type": "number",
-            "description": "The severity of the request (between 0 and 1)."
-        },
-        "metadata": {
-            "type": "object",
-            "description": "Additional metadata about the order."
-        }
-      },
-      "required": ["order_number", "customer_name", "related_tickets", "related_ticket_reasons", "severity"]
-    }
-  }