Description
Fixes the manual laser control widget so laser on/off commands are sent to the machine currently assigned to the widget, instead of relying on the globally active config machine.

Previously, clicking the manual laser button could enqueue set_focus_power() against the wrong machine context, which meant the selected laser did not turn on from the widget.

Changes

• Allow MachineCmd.set_power() and MachineCmd.set_focus_power() to accept an explicit machine.
• Update LaserControlWidget to pass its assigned machine when turning the laser on or off.
• Add focused tests for explicit machine routing in MachineCmd.

Verification

• python3 -m compileall passed for changed files.
• git diff --check passed.
• Could not run pixi run lint or targeted pytest locally because pixi and pytest are not available in this environment.