feat: add comprehensive test coverage for tools module

[maslinedwin]

Fixes #149

This PR adds comprehensive unit tests for the tools module, covering:

• web_search() with various configurations (domains, image options, location)
• x_search() with date ranges, handles, and media options
• code_execution() tool creation
• collections_search() with limits and instructions
• mcp() tool with labels, descriptions, authorization, and headers
• get_tool_call_type() for all supported tool types

Provides ~200 lines of test coverage for critical tool creation functions.