feat: order/delay in service files, enable cmd, --all on unit commands

- install/uninstall/start/stop/enable take <name> or --all; *all kept as shortcuts
- add enable (enable at boot + start); startall no longer enables
- order/delay resolved by config.ResolveOrder and written into systemd,
  OpenRC and runit service files (After=/sleep), so they apply at boot
- install --all stops and disables units before removing their files
- update regenerates all installed, enabled units and removes disabled ones
- edit creates the config dir; docs and man page updated
- tests: fake Init for cmd, ResolveOrder, backend ordering output

cmd/enable.go

@@ -0,0 +1,52 @@
+package cmd
+
+import (
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/spf13/cobra"
+	"github.com/warkanum/unitdore/config"
+	"github.com/warkanum/unitdore/initsys"
+)
+
+var enableAll bool
+
+var enableCmd = &cobra.Command{
+	Use:   "enable <name> | --all",
+	Short: "Enable at boot and start a unit (or all with --all)",
+	Long: `Enable enables the named installed unit at boot and starts it.
+
+With --all (same as 'enableall') it does so for every enabled, installed unit
+in startup order, like 'start --all'.`,
+	Args: nameOrAll(&enableAll),
+	RunE: func(cmd *cobra.Command, args []string) error {
+		cfg, ini, err := loadInit()
+		if err != nil {
+			return err
+		}
+		if enableAll {
+			bulkStart(cfg, ini, os.Stdout, initsys.Init.Enable, "enabled")
+			return nil
+		}
+		return enableOne(cfg, ini, args[0], os.Stdout)
+	},
+}
+
+func init() {
+	enableCmd.Flags().BoolVar(&enableAll, "all", false, "enable all enabled, installed units")
+	rootCmd.AddCommand(enableCmd)
+}
+
+func enableOne(cfg *config.Config, ini initsys.Init, name string, w io.Writer) error {
+	u, err := installedUnit(cfg, ini, name)
+	if err != nil {
+		return err
+	}
+	fmt.Fprintf(w, "  ▶ enabling %s...\n", ini.ServiceName(*u, cfg.Prefix, cfg.Suffix))
+	if err := ini.Enable(*u, cfg.Prefix, cfg.Suffix); err != nil {
+		return err
+	}
+	fmt.Fprintf(w, "  ✓ enabled: %s\n", name)
+	return nil
+}