Add prefix/suffix support, short ID fallback, unit docs

- config: add Prefix/Suffix fields to Config struct
- systemd: ServiceName/Generate/UnitPath/Install/Uninstall/Enable/Disable/Status all accept prefix+suffix
- runtime: fall back to short container ID (12 chars) when container has no name
- cmd: active, status, install all thread prefix/suffix from config
- systemd/generator_test.go: updated all calls + added TestGenerate_WithPrefixSuffix
- docs/generated-units.md: full examples of every unit type + ordering + naming
- README: updated config docs, prefix/suffix section, link to docs/

cmd/active.go

@@ -27,6 +27,8 @@ func runActive(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
+	prefix, suffix := cfg.Prefix, cfg.Suffix
+
 	// Sort by order then name for deterministic startup sequence
 	units := make([]config.Unit, len(cfg.Units))
 	copy(units, cfg.Units)
@@ -44,12 +46,12 @@ func runActive(cmd *cobra.Command, args []string) error {
 		if !u.Enabled {
 			continue
 		}
-		if !systemd.IsInstalled(u) {
+		if !systemd.IsInstalled(u, prefix, suffix) {
 			fmt.Printf("  ! %s: not installed — run 'unitdore install' first\n", u.Name)
 			continue
 		}
-		fmt.Printf("  ▶ enabling: %s...\n", systemd.ServiceName(u))
-		if err := systemd.Enable(u); err != nil {
+		fmt.Printf("  ▶ enabling: %s...\n", systemd.ServiceName(u, prefix, suffix))
+		if err := systemd.Enable(u, prefix, suffix); err != nil {
 			fmt.Printf("  ✗ failed: %s: %v\n", u.Name, err)
 			failed++
 		} else {