feat: add supervisor prototype with embedded frontend

internal/session/pty.go

@@ -0,0 +1,14 @@
+package session
+
+import "io"
+
+type PTYProcess interface {
+	io.ReadWriteCloser
+	Wait() error
+	Resize(cols, rows uint16) error
+	SignalStop() error
+}
+
+type PTYFactory interface {
+	Start(command string) (PTYProcess, error)
+}