fix the tool call but cause unreach model

[locnguyen1986]

fix the tool call but cause unreach model

[Copilot]

Pull request overview

This PR addresses two distinct issues: clearing ToolChoice when no tools are present to prevent provider validation errors, and refining error handling to properly distinguish between platform errors and LLM communication errors.

• Clears ToolChoice field when no tools are present in requests (both streaming and non-streaming)
• Adds explicit error handling for platform errors (NotFound, Forbidden, Unauthorized, Conflict) to prevent them from triggering fallback responses
• Adds support for tool_result content type in flexible content parts

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
services/llm-api/internal/utils/httpclients/chat/chat_completion_client.go	Added logic to clear ToolChoice when Tools array is empty in both CreateChatCompletion and doStreamingRequest methods
services/llm-api/internal/interfaces/httpserver/routes/v1/chat/completion_route.go	Added explicit error type handling for NotFound, Forbidden, Unauthorized, and Conflict errors before falling back to LLM error handling
services/llm-api/internal/interfaces/httpserver/requests/chat/chat.go	Added support for tool_result content type, converting it to text parts for OpenAI compatibility
services/llm-api/internal/interfaces/httpserver/handlers/chathandler/chat_handler.go	Updated error message for conversation not found to be more user-friendly

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