v8 boundary: callbacks native→JS

[cs01]

Native code passes a ChadScript function to pragma code. Pragma invokes it (EventEmitter, express middleware).

Ask

• Register native fn pointer via V8 FunctionTemplate
• JS call → C trampoline → native fn
• Lifetime: native fn must outlive V8 hold; Boehm finalizer coordination
• Thread-safety: single-threaded v1 is fine

Est

~1-2 weeks. Load-bearing for express/ws/EventEmitter-style libs. Not needed for pure data libs.