Function emit_parsed_frames 

fn emit_parsed_frames(
    parser: &mut ControlStreamParser,
    data: &[u8],
    refused_seen: &mut u64,
    side: ProxySide,
    ctx: &ForwardCtx,
    report: &Reporter<'_>,
)

Feed bytes to the control parser and emit observer events for any completed frames.

The hook is deliberately not invoked here — on the pass-through path the bytes have already been forwarded, so an Action returned there would be unexecutable. Hooks that need to see control messages without rewriting them should be implemented as a ProxyObserver; hooks that need to rewrite them declare Interest::CONTROL, which routes traffic through pipe_control_mutating instead.