feat: Add LOCAL variable support for responses with UTF-8 JSON encoding.

Description: This feature adds support for UTF-8 encoding in JSON responses, allowing for proper handling of special characters and emojis.

- Implement unit tests for UTF-8 encoding in various model providers including Gemini, OpenAI, and OpenAI Compatible.
- Validate UTF-8 support in token counting, content generation, and error handling.
- Introduce tests for JSON serialization ensuring proper handling of French characters and emojis.
- Create tests for language instruction generation based on locale settings.
- Validate UTF-8 handling in workflow tools including AnalyzeTool, CodereviewTool, and DebugIssueTool.
- Ensure that all tests check for correct UTF-8 character preservation and proper JSON formatting.
- Add integration tests to verify the interaction between locale settings and model responses.

tools/simple/base.py

@@ -372,24 +372,24 @@ class SimpleTool(BaseTool):
 
                 follow_up_instructions = get_follow_up_instructions(0)
                 prompt = f"{prompt}\n\n{follow_up_instructions}"
-                logger.debug(f"Added follow-up instructions for new {self.get_name()} conversation")
-
-            # Validate images if any were provided
+                logger.debug(f"Added follow-up instructions for new {self.get_name()} conversation")            # Validate images if any were provided
             if images:
                 image_validation_error = self._validate_image_limits(
                     images, model_context=self._model_context, continuation_id=continuation_id
                 )
                 if image_validation_error:
-                    return [TextContent(type="text", text=json.dumps(image_validation_error))]
+                    return [TextContent(
+                        type="text", 
+                        text=json.dumps(image_validation_error, ensure_ascii=False)
+                    )]
 
             # Get and validate temperature against model constraints
             temperature, temp_warnings = self.get_validated_temperature(request, self._model_context)
 
             # Log any temperature corrections
             for warning in temp_warnings:
+                # Get thinking mode with defaults
                 logger.warning(warning)
-
-            # Get thinking mode with defaults
             thinking_mode = self.get_request_thinking_mode(request)
             if thinking_mode is None:
                 thinking_mode = self.get_default_thinking_mode()
@@ -398,7 +398,9 @@ class SimpleTool(BaseTool):
             provider = self._model_context.provider
 
             # Get system prompt for this tool
-            system_prompt = self.get_system_prompt()
+            base_system_prompt = self.get_system_prompt()
+            language_instruction = self.get_language_instruction()
+            system_prompt = language_instruction + base_system_prompt
 
             # Generate AI response using the provider
             logger.info(f"Sending request to {provider.get_provider_type().value} API for {self.get_name()}")