feat(robot_driver): add tool GPIO get/set to RobotDriver

[erwinkendo]

This PR adds a generic interface to RobotDriver for controlling the digital outputs on a robot's tool (wrist) connector.

This functionality was originally developed against SmartArmStack/sas_core. It is ported here because the C++ core now lives in sas_cpp.

Changes

• include/marinholab/sas/core/sas_robot_driver.hpp
  • New protected member std::array<bool, 2> tool_gpio_{} (value-initialised to {false, false}).
  • New virtual methods get_tool_gpio() and set_tool_gpio(const std::array<bool, 2>&).
  • Added #include <array>.
• src/sas_robot_driver.cpp
  • Default implementations that store and return tool_gpio_. Concrete drivers override them to command the hardware.
• examples/sas_robot_driver_example_main.cpp
  • Checks the {false, false} default and a set/get round-trip, throwing on failure, so the check also runs in Release builds. docker/build.sh runs this example, so CI covers it.
• Contributors sections updated.

Backwards compatibility

The methods are virtual and have default implementations, so existing drivers build and behave exactly as before.

Related PRs

This change is used by follow-up changes on these branches. PRs will be opened once this one is merged and released:

1. Python bindings: https://github.com/erwinkendo/sas_py/tree/feature/tool_gpio
2. ROS server/client: https://github.com/erwinkendo/sas_robot_driver/tree/feature/tool_gpio
3. UR driver: https://github.com/erwinkendo/sas_robot_driver_ur/tree/feature/tool_gpio

PRs 2 and 3 need a libmarinholab-sas-core release that includes this change.

Testing

• Built with -Wall -Wextra -Wpedantic. No new warnings.
• sas_robot_driver_example passes the new tool GPIO checks.
• End-to-end tests were run with https://github.com/erwinkendo/sas_robot_driver_tester, which builds this branch from source together with the sas_robot_driver and sas_robot_driver_ur branches (see PR 4).

Open question

The array size is fixed at 2 to match the UR wrist connector. If you'd prefer to keep this robot-agnostic, I can change it to std::vector<bool> or a template size.