1.3.7: Trainer: remove TARGET label and highlight active target ring (#104)
Motivation
Simplify trainer-mode UI by removing the redundant "TARGET" text and provide clearer feedback by changing the target ring color while the target note is active.
Description
Updated drawTargetNotes to accept an activeNotes map and removed the TARGET text label, drawing only the ring instead.
Ring stroke color now switches to a highlighting color when the target MIDI note is present in the provided activeNotes.