fix(types): revert make_valid_bedrock_tool_use_id to str -> str

CI mypy failed on the Optional[str] annotation greptile suggested in #28825:

  factory.py:4033 - Incompatible types (expression has type 'str | None',
    TypedDict item 'toolUseId' has type 'str')
  (and two more at the same call sites)

Downstream BedrockToolUseBlock and BedrockToolResultBlock require str.
The sibling make_valid_bedrock_tool_name has the same None-passthrough
and the same str -> str annotation for the same reason; keeping symmetry.

Restored the # type: ignore[arg-type] on the empty-passthrough test with
a comment explaining the signature trade-off.

litellm/litellm_core_utils/prompt_templates/factory.py

@@ -5361,9 +5361,7 @@ def make_valid_bedrock_tool_name(input_tool_name: str) -> str:
     return valid_string
 
 
-def make_valid_bedrock_tool_use_id(
-    input_tool_use_id: Optional[str],
-) -> Optional[str]:
+def make_valid_bedrock_tool_use_id(input_tool_use_id: str) -> str:
     """
     Replaces any invalid characters in the input tool_use_id with underscores
     so it matches Bedrock Converse's required pattern ``^[a-zA-Z0-9_.:-]+$``.

tests/test_litellm/litellm_core_utils/prompt_templates/test_litellm_core_utils_prompt_templates_factory.py

@@ -2818,7 +2818,12 @@ def test_make_valid_bedrock_tool_use_id_empty_passthrough():
     )
 
     assert make_valid_bedrock_tool_use_id("") == ""
-    assert make_valid_bedrock_tool_use_id(None) is None
+    # The signature is ``str -> str`` to match downstream TypedDict callers
+    # (``BedrockToolUseBlock.toolUseId``); the helper still defensively returns
+    # the input unchanged when None slips in. Suppress the resulting mypy
+    # error here — annotating the helper as ``Optional[str]`` would force a
+    # cascade of ``cast(str, ...)`` calls at the use sites.
+    assert make_valid_bedrock_tool_use_id(None) is None  # type: ignore[arg-type]
 
 
 def test_bedrock_tool_call_invoke_sanitizes_drifted_name_and_id():