Wait-free impulse-response mailbox for the JUCE convolver, chunked
processBlock for oversized host buffers, SafePointer in the add menu,
runner state machine that survives apply/stop/restart during applying,
consume-by-rename for spool results, debounce only while running,
membership-based entering-slot detection, solo cleared when its slot
leaves the chain, EQ gestures end on the parameters they began on, and
a solo test that exercises a slot actually in the chain.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>