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>

letta/local_llm/function_parser.py

@@ -1,68 +0,0 @@
-import copy
-import json
-
-from letta.helpers.json_helpers import json_dumps, json_loads
-
-NO_HEARTBEAT_FUNCS = ["send_message"]
-
-
-def insert_heartbeat(message):
-    # message_copy = message.copy()
-    message_copy = copy.deepcopy(message)
-
-    if message_copy.get("function_call"):
-        # function_name = message.get("function_call").get("name")
-        params = message_copy.get("function_call").get("arguments")
-        params = json_loads(params)
-        params["request_heartbeat"] = True
-        message_copy["function_call"]["arguments"] = json_dumps(params)
-
-    elif message_copy.get("tool_call"):
-        # function_name = message.get("tool_calls")[0].get("function").get("name")
-        params = message_copy.get("tool_calls")[0].get("function").get("arguments")
-        params = json_loads(params)
-        params["request_heartbeat"] = True
-        message_copy["tools_calls"][0]["function"]["arguments"] = json_dumps(params)
-
-    return message_copy
-
-
-def heartbeat_correction(message_history, new_message):
-    """Add heartbeats where we think the agent forgot to add them themselves
-
-    If the last message in the stack is a user message and the new message is an assistant func call, fix the heartbeat
-
-    See: https://github.com/letta-ai/letta/issues/601
-    """
-    if len(message_history) < 1:
-        return None
-
-    last_message_was_user = False
-    if message_history[-1]["role"] == "user":
-        try:
-            content = json_loads(message_history[-1]["content"])
-        except json.JSONDecodeError:
-            return None
-        # Check if it's a user message or system message
-        if content["type"] == "user_message":
-            last_message_was_user = True
-
-    new_message_is_heartbeat_function = False
-    if new_message["role"] == "assistant":
-        if new_message.get("function_call") or new_message.get("tool_calls"):
-            if new_message.get("function_call"):
-                function_name = new_message.get("function_call").get("name")
-            elif new_message.get("tool_calls"):
-                function_name = new_message.get("tool_calls")[0].get("function").get("name")
-            if function_name not in NO_HEARTBEAT_FUNCS:
-                new_message_is_heartbeat_function = True
-
-    if last_message_was_user and new_message_is_heartbeat_function:
-        return insert_heartbeat(new_message)
-    else:
-        return None
-
-
-def patch_function(message_history, new_message):
-    corrected_output = heartbeat_correction(message_history=message_history, new_message=new_message)
-    return corrected_output if corrected_output is not None else new_message