feat: script and exec runtimes with configurable shell

Add runtime: script (shell file, default /bin/bash, optional stop_script) and runtime: exec (executable with args, optional stop_executable). Both support service_type simple|oneshot and working_dir.

config/config.go

@@ -21,6 +21,14 @@ const (
 	KindStack     = "stack"
 )
 
+// Runtimes for units that are not containers.
+const (
+	RuntimeScript = "script" // run a shell script
+	RuntimeExec   = "exec"   // run an executable directly
+
+	DefaultShell = "/bin/bash"
+)
+
 // Unit represents a single managed container unit.
 type Unit struct {
 	Name           string `yaml:"name"`
@@ -41,11 +49,38 @@ type Unit struct {
 	WorkingDir   string   `yaml:"working_dir,omitempty"`   // compose project directory
 	ComposeFiles []string `yaml:"compose_files,omitempty"` // relative to working_dir unless absolute
 	ComposeBin   string   `yaml:"compose_bin,omitempty"`   // path to podman-compose
+
+	// Script fields (runtime: script) — run a shell file as a service.
+	Script     string `yaml:"script,omitempty"`      // path to script run as ExecStart
+	StopScript string `yaml:"stop_script,omitempty"` // optional script run as ExecStop
+	Shell      string `yaml:"shell,omitempty"`       // interpreter, default /bin/bash
+
+	// Executable fields (runtime: exec) — run a binary directly.
+	Executable     string   `yaml:"executable,omitempty"`      // path to binary run as ExecStart
+	Args           []string `yaml:"args,omitempty"`            // arguments for executable
+	StopExecutable string   `yaml:"stop_executable,omitempty"` // optional binary run as ExecStop
+
+	// Script and exec units: simple (default) | oneshot. WorkingDir is also used.
+	ServiceType string `yaml:"service_type,omitempty"`
 }
 
 // IsStack reports whether the unit manages a compose stack.
 func (u Unit) IsStack() bool { return u.Kind == KindStack }
 
+// IsScript reports whether the unit runs a shell script.
+func (u Unit) IsScript() bool { return u.Runtime == RuntimeScript }
+
+// IsExec reports whether the unit runs an executable directly.
+func (u Unit) IsExec() bool { return u.Runtime == RuntimeExec }
+
+// ShellPath returns the configured interpreter, or the default.
+func (u Unit) ShellPath() string {
+	if u.Shell == "" {
+		return DefaultShell
+	}
+	return u.Shell
+}
+
 // Config is the root config structure.
 type Config struct {
 	Units  []Unit   `yaml:"units"`