86: Add default limit for tools completions

[rhys117]

Resolves #86

Purpose

Introduces a configurable limit on tool completions to prevent infinite loops and excessive API usage. This feature adds protection against scenarios where AI responses might trigger continuous tool calls.

Implementation Details

• Added max_tool_completions configuration option (default: 25 calls)
• Added per-chat override capability through RubyLLM.chat(max_tool_completions: N)
• Implemented ToolCallCompletionsReachedError when limit is exceeded
• Added tracking of tool completions via number_of_tool_completions counter
• Can be overridden for unlimited tool completions with nil

Usage Example

# Global configuration
RubyLLM.configure do |config|
  config.max_tool_completions = 10  # Set default limit
end

# Per-chat override
chat = RubyLLM.chat(max_tool_completions: 15)

Testing

• Added RSpec test cases for OpenAI + Claude
• Verified both global configuration and per-chat override functionality
• Confirmed error raised when limit is reached

Documentation

• Added section in tools.md guide explaining the feature
• Included examples for both global and per-chat configuration

TODO

• Add VCR cassettes for testing with additional providers (I do not have API keys for these providers):
  • Anthropic
  • Gemini
• Review error messaging for clarity

[rhys117]

It might be worth discussing if this should be handled via the chat instead of raising an unhandled error.