test: Add comprehensive test coverage for DefaultToolCallingManager

[alxkm]

Description

This PR adds critical test coverage for DefaultToolCallingManager to ensure robust handling of common production scenarios and prevent runtime failures.

Changes

Added 3 essential test cases to DefaultToolCallingManagerTest:

• Multiple tool calls: Validates handling of multiple tool invocations in a single response - a very common pattern when AI models need to call several tools
• Complex JSON arguments: Tests nested objects and arrays in tool parameters to ensure proper handling of sophisticated tool schemas
• Malformed JSON handling: Ensures graceful degradation when AI models generate invalid JSON, preventing crashes in production

Impact

The existing tests only covered null/empty argument scenarios. These additional tests are important for:

• Production stability: These scenarios will occur in production environments
• Core functionality: Multiple tool calling is a fundamental feature that must work correctly
• Error resilience: AI models can and will generate malformed JSON that must be handled gracefully
• Real-world usage: Complex JSON structures are common in production tool schemas

[ilayaperumalg]

@alxkm Thanks for the PR and @sunyuhan1998 thanks for the review. Rebased and merged as d148ca2