Reverb Send
INTERNAL fragment (Stage 4 F2) — the first AUDIO-THROUGH lane send: a parallel reverb AUX. The lane's per-voice tap is fed into `in` (a unity gain) → a fully-wet `reverb` → `out` (the return level), and audio.js wires `out` to the kit bus. Because the reverb is 100% wet and the lane's DRY signal still reaches the bus through its own tap, this is a true parallel send (dry untouched, wet added). Unlike the rumble send (whose env-follower consumes the tap as a CV trigger), here the lane's real audio FLOWS THROUGH the chain — proving the registry + the generic boundary carry a non-CV send. Macros: Size (tail length), Tone (damping), Wet (return level). `hidden`, expanded only by add_drum_lane_send { send: 'reverb-send' }.