feat(copilot): replace LangGraph config with request-scoped context variables

- Refactor `llm_call` and `generate_title` nodes to retrieve `llm_config` from request-scoped context variable instead of LangGraph config
- Remove `jwt_token` and `llm_config` from LangGraph configurable parameters in `AgentService.stream`
- Add `set_current_llm_config` and `get_current_llm_config` functions to `connector_factory` and export them in `__init__.py`
- Update `tool_node` to no longer extract `jwt_token` from config as it is now handled via context variable
- Improves thread safety and decouples configuration from LangGraph's state management

gns3server/agent/gns3_copilot/gns3_client/__init__.py

@@ -27,6 +27,8 @@ from .connector_factory import (
     get_llm_config,
     set_current_jwt_token,
     get_current_jwt_token,
+    set_current_llm_config,
+    get_current_llm_config,
 )
 from .custom_gns3fy import (
     CONSOLE_TYPES,
@@ -66,4 +68,6 @@ __all__ = [
     "get_llm_config",
     "set_current_jwt_token",
     "get_current_jwt_token",
+    "set_current_llm_config",
+    "get_current_llm_config",
 ]