Require secret at the commit that drops go-bip39 (closes #70)

sneak/secret now carries its own copy of go-bip39
(sneak/secret#130), so requiring it at that
commit, ef0ae90, lets go mod tidy drop go-bip39 from go.sum. Earlier,
secret renamed its module to sneak.berlin/go/secret
(sneak/secret#43), so the requirement, the
two imports of its bip85 package and the README sentence naming that
package move to the new path. The bip85 functions keyfunc calls are
unchanged, and no other requirement moves.

Model: opus-5-5

go.mod

@@ -4,13 +4,13 @@ go 1.26.0
 
 require (
 	filippo.io/age v1.3.2
-	git.eeqj.de/sneak/secret v0.0.0-20260810132333-41cea400a7fd
 	github.com/btcsuite/btcd v0.25.0
 	github.com/btcsuite/btcd/btcutil v1.2.0
 	github.com/spf13/cobra v1.10.2
 	github.com/stretchr/testify v1.12.1
 	golang.org/x/crypto v0.57.0
 	golang.org/x/term v0.46.0
+	sneak.berlin/go/secret v0.0.0-20261007105610-ef0ae90768c8
 )
 
 require (