Support OpenAI standard tool_choice parameter

Venice API rejects the tool_choice parameter, breaking compatibility with AI development tools that follow OpenAI's standard format.

When sending tool_choice: "auto", Venice returns: Error 400: "auto" tool choice requires --enable-auto-tool-choice and --tool-call-parser to be set

This prevents Venice from working with:

• Kilo Code (tool-calling coding agent)

• Cursor (AI-powered IDE)

• OpenClaw (similar issues #22115, #14281)

• Home Assistant integrations (#284)

• Any tool using OpenAI SDKs

Confirmed working: Venice supports function calling when tool_choice is omitted. The issue is solely the parameter rejection.

Request: Enable server-side support for tool_choice to match OpenAI's specification. This parameter has been standard since 2023.

Note: Kilo Code is a tool-calling agent that requires tools for all file operations, command execution, and workflow control. It will not change this architectural design. Venice must support standard OpenAI workflow for compatibility.

Technical context: tool_choice values are "auto" (model decides), "none" (no tools), "required" (force tools), or specific function selection.

This would make Venice accessible to a much wider developer ecosystem.