treewide: include PipeWire op and enforce PulseAudio check

This fully replaces PulseAudio with PipeWire and enforces the PulseAudio check and error message. The pipewire-pulse daemon is handled in the NixOS module.

Closes #26.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/outcome/sppulse.go

@@ -29,7 +29,7 @@ type spPulseOp struct {
 }
 
 func (s *spPulseOp) toSystem(state *outcomeStateSys) error {
-	if state.et&hst.EPulse == 0 {
+	if !state.directPulse || state.et&hst.EPulse == 0 {
 		return errNotEnabled
 	}