feat

- implemented spellcaster

internal/models/models.go

@@ -14,12 +14,14 @@ type Spell struct {
 type SpellCast struct {
 	Spell  Spell
 	Args   map[string]string
+	Stdin  io.Reader
 	Stdout io.Writer
 	Stderr io.Writer
 }
 
 type CastResult struct {
 	ExitCode int
+	Err      error
 	Duration time.Duration
 	Meta     map[string]any
 }