refactor: move string_hash function to internal.py

The string_hash utility function was defined in context.py but belongs
with other utility functions in internal.py. This improves code
organization.

Author: leavesster

oocana/oocana/context.py

@@ -10,21 +10,14 @@
 from .throttler import throttle
 from .preview import PreviewPayload, DataFrame, PreviewPayloadInternal, ShapeDataFrame
 from .data import EXECUTOR_NAME
-from .internal import random_string, InternalAPI
+from .internal import random_string, InternalAPI, string_hash
 from .credential import CredentialInput
 import os.path
 import logging
-import hashlib
 
 __all__ = ["Context", "HandleDefDict", "BlockJob", "BlockExecuteException"]
 
 
-def string_hash(text: str) -> str:
-    """
-    Generates a deterministic hash for a given string.
-    """
-    return hashlib.sha256(text.encode('utf-8')).hexdigest()
-
 class ToNode(TypedDict):
     node_id: str
 

oocana/oocana/internal.py

@@ -3,6 +3,8 @@
 import random
 import string
 import math
+import hashlib
+
 
 class InternalAPI:
 
@@ -30,3 +32,10 @@ async def update_node_weight(self, node_id: str, weight: int | float) -> None:
 
 def random_string(length=8):
     return ''.join(random.choices(string.ascii_letters + string.digits, k=length))
+
+
+def string_hash(text: str) -> str:
+    """
+    Generates a deterministic hash for a given string.
+    """
+    return hashlib.sha256(text.encode('utf-8')).hexdigest()