Add AGC, API contract, and E2E tests for refactoring protection

Add critical hardware tests for real-world breakage scenarios

Expand test suite to ~170 tests across 3 tiers

Add remote hardware testing via SSH and redesign motion accuracy tests

Fix hardware test cascade: isolate audio tests, skip on mic failure

Add deep pipeline integration tests for hardware suite

Add audio playback test to hardware suite

Improve testing: verbose output, web coverage panel, hardware tests

Add test documentation, runner script, and coverage matrix