Remove cbk and mnemonic commands from sutil

sutil holds only the utilities wanted on every machine; it is not a
command-line front end for the packages in pkg/. cbk and bip39wordlist
remain libraries with no CLI surface. The README states the boundary.

internal/cli/generate.go

@@ -8,7 +8,6 @@ import (
 
 	"sneak.berlin/go/x/internal/pwgen"
 	"sneak.berlin/go/x/internal/randstream"
-	"sneak.berlin/go/x/pkg/bip39wordlist"
 )
 
 // streamChunkSize is the write size used by `generate random`. Large
@@ -21,13 +20,12 @@ func newGenerateCommand() *cobra.Command {
 	cmd := &cobra.Command{
 		Use:     "generate",
 		Aliases: []string{"gen"},
-		Short:   "Generate random bytes, passwords, and mnemonics",
+		Short:   "Generate random bytes and passwords",
 	}
 
 	cmd.AddCommand(
 		newGenerateRandomCommand(),
 		newGeneratePasswordCommand(),
-		newGenerateMnemonicCommand(),
 	)
 
 	return cmd
@@ -107,36 +105,6 @@ no usable word list.`,
 	}
 }
 
-// newGenerateMnemonicCommand returns `sutil generate mnemonic`.
-func newGenerateMnemonicCommand() *cobra.Command {
-	var wordCount int
-
-	cmd := &cobra.Command{
-		Use:   "mnemonic",
-		Short: "Print a new random BIP39 mnemonic phrase",
-		Long: `Prints a new BIP39 mnemonic phrase generated from crypto/rand. The
-default of 24 words encodes 256 bits of entropy; 12 words encodes 128.`,
-		Args: cobra.NoArgs,
-		RunE: func(cmd *cobra.Command, _ []string) error {
-			mnemonic, err := bip39wordlist.GenerateMnemonic(wordCount)
-			if err != nil {
-				return err
-			}
-
-			_, err = fmt.Fprintln(cmd.OutOrStdout(), mnemonic)
-
-			return err
-		},
-	}
-
-	cmd.Flags().IntVarP(
-		&wordCount, "words", "w", bip39wordlist.MaxWordCount,
-		"number of words: 12, 15, 18, 21, or 24",
-	)
-
-	return cmd
-}
-
 // streamBytes copies limit bytes (or everything, when limit is zero) from
 // src to dst in streamChunkSize chunks.
 func streamBytes(dst io.Writer, src io.Reader, limit int64) error {