MAX_OUTPUT_CHARS, MAX_READ_CHARS, and MAX_DIFF_LINES are now
defined once in src/constants.py and imported by the three files
that previously duplicated them (tool_execution.py,
tool_implementations.py, agent_tools.py). agent_tools.py re-exports
them for backward compatibility.
Co-authored-by: mcnoliveira <mcnoliveira@gmail.com>