feat: add comprehensive mock tests for sequential tool calling

- Created test suite covering various sequential tool calling scenarios
- Added tests for basic sequential, multi-tool sequences, dependencies
- Included tests for streaming, error handling, and different providers
- Added context preservation and complex argument tests
- Fixed import paths and Agent initialization format
- Corrected Ollama format to use JSON strings

Co-authored-by: Mervin Praison <MervinPraison@users.noreply.github.com>

Author: claude[bot]