tests: Add board qualification tests for buzzer.

[nedseb]

Summary

Closes #87
Depends on #89 (framework extension)

Adds board qualification tests for the audio buzzer (SMT-0825-S-HT-R) connected via PWM on SPEAKER (PA11).

Scenario: tests/scenarios/board_buzzer.yaml

Test	Description	Type
Buzzer tone 440Hz	Generate 440Hz tone for 500ms via PWM	hardware_script
Buzzer 440Hz audible	Manual confirmation of audible tone	manual
Buzzer frequency sweep	Sweep 200Hz→2000Hz in 100Hz steps	hardware_script
Buzzer sweep audible	Manual confirmation of sweep sound	manual

How to test

# Mock tests (no regression)
pytest tests/ -k mock

# Collect buzzer board tests
pytest tests/ -k board_buzzer --collect-only

# Run on hardware (requires STeaMi board, interactive)
pytest tests/ --port /dev/ttyACM0 -k board_buzzer -s

Test results

$ pytest tests/ -k mock -q
41 passed, 95 deselected

$ pytest tests/ -k board_buzzer --collect-only -q
4 tests collected (440Hz, audible, sweep, sweep audible)

$ pytest tests/ -k board_buzzer -q  # (sans --port)
4 skipped  # correctly skipped without hardware

Hardware test results will be added after board validation.

Test plan

• ruff check tests/ — passed
• pytest tests/ -k mock — 41 passed (no regression)
• 4 buzzer board tests correctly collected and skipped without --port
• Hardware validation on STeaMi board (pending)

[Copilot]

Pull request overview

Adds a new board-level qualification scenario for validating the STeaMi board’s PWM-driven audio buzzer on the SPEAKER pin, using the recently-added type: board scenario support.

Changes:

• Introduce a new type: board YAML scenario dedicated to the buzzer.
• Add two PWM-driven hardware scripts (440Hz tone + frequency sweep).
• Add two manual confirmation steps for audible validation (tone + sweep).

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