Fix: add stub implementations for non-ARM platforms to fix lint

Adds cgo_source_stub.go with inverse build tag (!linux || (!arm && !arm64))
to provide stub function signatures for CI linting on amd64 runners.

internal/audio/cgo_source_stub.go

@@ -0,0 +1,35 @@
+//go:build !linux || (!arm && !arm64)
+
+package audio
+
+// Stub implementations for non-ARM Linux platforms
+
+type CgoSource struct{}
+
+func NewCgoOutputSource(alsaDevice string) *CgoSource {
+	panic("audio CGO source not supported on this platform")
+}
+
+func NewCgoInputSource(alsaDevice string) *CgoSource {
+	panic("audio CGO source not supported on this platform")
+}
+
+func (c *CgoSource) Connect() error {
+	panic("audio CGO source not supported on this platform")
+}
+
+func (c *CgoSource) Disconnect() {
+	panic("audio CGO source not supported on this platform")
+}
+
+func (c *CgoSource) IsConnected() bool {
+	panic("audio CGO source not supported on this platform")
+}
+
+func (c *CgoSource) ReadMessage() (uint8, []byte, error) {
+	panic("audio CGO source not supported on this platform")
+}
+
+func (c *CgoSource) WriteMessage(msgType uint8, payload []byte) error {
+	panic("audio CGO source not supported on this platform")
+}