Fix missing toolbox-core dependency in Toolbox Agent documentation

[designcomputer]

Summary

Updated the Toolbox Agent documentation to address a critical missing dependency that prevents the agent from running successfully.

Changes Made

• Added missing dependency: Documented that toolbox-core must be installed via pip install toolbox-core
• Improved documentation structure: Added clear section numbering and better organization
• Enhanced readability: Fixed grammar, capitalization, and formatting throughout
• Added Prerequisites section: Set clear expectations before installation begins
• Clarified optional steps: Made it clearer when database creation can be skipped

Problem Solved

The original documentation was missing a crucial step - installing the toolbox-core package. Without this dependency, users encounter an ImportError: No module named 'toolbox-core' when trying to use the ToolboxToolset class in ADK. This fix ensures users can successfully set up and run the agent without encountering import errors.

Testing

• Verified the installation steps work correctly with the added dependency
• Confirmed the agent runs successfully after following the updated documentation