feat: podman-compose stack units and root/user execution scopes

- syncup: podman first, docker only as fallback (podman wins on name clash;
  existing docker units found in podman switch to podman)
- syncup: group podman-compose containers into one `kind: stack` unit per
  project (project, working_dir, compose_files, compose_bin from labels);
  disable existing member units ("part of stack <project>")
- generator: compose mode (podman-compose up/stop, WorkingDirectory) with
  pod start/stop fallback when compose binary/dir/files are missing
- reconcile: stacks disabled with "stack not found" when neither compose
  files nor pod exist
- root: scan root + rootless users listed in `users:` (podman only)
- non-root: config ~/.config/unitdore/units.yaml, own user units only
- sysuser package: runuser with XDG_RUNTIME_DIR/DBUS env, home/linger lookup
- install: warn when linger is not enabled for user units
- testdata/stack: podman-compose test stack and captured podman ps fixture
- docs: README, generated-units, man page, AGENTS, PLAN

cmd/root.go

@@ -5,6 +5,8 @@ import (
 	"os"
 
 	"github.com/spf13/cobra"
+	"github.com/warkanum/unitdore/config"
+	"github.com/warkanum/unitdore/sysuser"
 )
 
 var version = "0.0.10"
@@ -16,9 +18,23 @@ var rootCmd = &cobra.Command{
 	Short: "A door you open and close for container units",
 	Long: `Unitdore manages container units via systemd.
 
-It discovers running containers, stores them in a config file,
-and generates + manages systemd .service units for each one.`,
+It discovers running containers and podman-compose stacks, stores them in a
+config file, and generates + manages systemd .service units for each one.
+
+As root: system units, plus user units for users listed in 'users:'.
+As a normal user: own config and user units only.`,
 	Version: version,
+	PersistentPreRunE: func(cmd *cobra.Command, args []string) error {
+		// Normal users get their own config and manage only their user units
+		if !cmd.Flags().Changed("config") && !sysuser.IsRoot() {
+			home, err := sysuser.HomeDir(sysuser.Current())
+			if err != nil {
+				return err
+			}
+			configPath = config.UserConfigPath(home)
+		}
+		return nil
+	},
 }
 
 func Execute() {
@@ -29,5 +45,5 @@ func Execute() {
 }
 
 func init() {
-	rootCmd.PersistentFlags().StringVar(&configPath, "config", "/etc/unitdore/units.yaml", "path to units config file")
+	rootCmd.PersistentFlags().StringVar(&configPath, "config", config.DefaultConfigPath, "path to units config file (default for non-root: ~/.config/unitdore/units.yaml)")
 }