feat(dispatch): launch interactive menu on no-arg TTY invocation

internal/dispatch/dispatch.go

@@ -17,6 +17,7 @@ import (
 
 	"git.westgate.pw/ShadowsOverWestgate/sow-tools/internal/app"
 	"git.westgate.pw/ShadowsOverWestgate/sow-tools/internal/buildinfo"
+	"git.westgate.pw/ShadowsOverWestgate/sow-tools/internal/menu"
 )
 
 // Exit codes follow the sysexits(3) convention so CI can distinguish
@@ -103,8 +104,52 @@ func find(name string) (Builder, bool) {
 	return Builder{}, false
 }
 
-// Main is the `crucible` dispatcher entrypoint.
-func Main(args []string) int { return run(args, os.Stdout, os.Stderr) }
+// Main is the `crucible` dispatcher entrypoint. With no arguments on an
+// interactive terminal it launches the menu; otherwise (pipes, CI) it prints
+// usage, preserving scriptable behavior.
+func Main(args []string) int {
+	if len(args) == 0 && interactive(os.Stdout) {
+		return runMenu(os.Stdout, os.Stderr, os.Stdin)
+	}
+	return run(args, os.Stdout, os.Stderr)
+}
+
+func interactive(f *os.File) bool {
+	fi, err := f.Stat()
+	if err != nil {
+		return false
+	}
+	return fi.Mode()&os.ModeCharDevice != 0
+}
+
+func menuItems() []menu.Item {
+	var items []menu.Item
+	for _, b := range Registry {
+		if !b.Wired {
+			continue
+		}
+		for _, sub := range b.subcommands() {
+			items = append(items, menu.Item{
+				Label: b.Name + " " + sub,
+				Desc:  b.Summary,
+				Args:  []string{b.Name, sub},
+			})
+		}
+	}
+	return items
+}
+
+func runMenu(out, errw io.Writer, in io.Reader) int {
+	chosen, err := menu.Select(out, in, menuItems())
+	if err != nil {
+		fmt.Fprintln(errw, "crucible:", err)
+		return exitUsage
+	}
+	if chosen == nil {
+		return exitOK
+	}
+	return run(chosen, out, errw)
+}
 
 // RunBuilder is the standalone `crucible-<name>` entrypoint.
 func RunBuilder(name string, args []string) int {