tests: Add board qualification tests for A/B/Menu buttons.

[nedseb]

Description

Add board qualification tests for the A, B, and Menu buttons on the STeaMi board. These buttons are directly connected to STM32WB55 GPIO pins (not via the I/O expander like the D-PAD).

Components

Button	Pin name	STM32WB55 Pin
A	A_BUTTON	PA7
B	B_BUTTON	PA8
Menu	MENU_BUTTON	PA0

Note: D-PAD buttons (UP/DOWN/LEFT/RIGHT) are already tested in mcp23009e.yaml via the I/O expander.

Scenario: tests/scenarios/board_buttons.yaml

Tests

For each button (A, B, Menu):

1. Prompt the operator to press the button when the green LED lights up
2. Poll the button state for 5 seconds with LED_GREEN as indicator
3. Verify the button press was detected (active low with pull-up)

All tests use hardware_script action with pre_prompt (hardware mode only, interactive).

Depends on

• tests: Extend test framework for driverless board qualification scenarios. #83 (framework extension for `type: board` scenarios)