feat: replace IO type imports with string literals

Remove direct imports of IO type constants from comfy.comfy_types and replace them with string literals "STRING" in input type definitions and return types. This improves code portability and reduces dependency on external type definitions.

Changes made across multiple files:
- Remove `from comfy.comfy_types import IO` imports
- Replace `IO.STRING` with "STRING" in INPUT_TYPES and RETURN_TYPES
- Move CLIPTextEncode import to function scope in prompt.py for better dependency management

This refactor maintains the same functionality while making the code more self-contained and reducing external dependencies.

py/nodes/lora_stacker.py

@@ -1,4 +1,3 @@
-from comfy.comfy_types import IO # type: ignore
 import os
 from ..utils.utils import get_lora_info
 from .utils import FlexibleOptionalInputType, any_type, extract_lora_name, get_loras_list
@@ -15,7 +14,7 @@ class LoraStacker:
     def INPUT_TYPES(cls):
         return {
             "required": {
-                "text": (IO.STRING, {
+                "text": ("STRING", {
                     "multiline": True, 
                     "pysssss.autocomplete": False, 
                     "dynamicPrompts": True, 
@@ -26,7 +25,7 @@ class LoraStacker:
             "optional": FlexibleOptionalInputType(any_type),
         }
 
-    RETURN_TYPES = ("LORA_STACK", IO.STRING, IO.STRING)
+    RETURN_TYPES = ("LORA_STACK", "STRING", "STRING")
     RETURN_NAMES = ("LORA_STACK", "trigger_words", "active_loras")
     FUNCTION = "stack_loras"