Copy go-bip39 into internal/bip39 (closes #42)

go-bip39's repository no longer exists, so keyfunc now carries the
part of v1.1.0 it uses, with the upstream LICENSE beside it, and
imports it from internal/bip39. Upstream's tests and test vectors for
the kept code come along unchanged; where they called a removed
function, crypto/rand stands in for NewEntropy and EntropyFromMnemonic
for MnemonicToByteArray.

Changes beyond the trimming are what the linter asked for: the
package-level variables moved into the functions that use them, three
error strings were lower-cased, and the unknown-word error now wraps
ErrInvalidMnemonic.

go.mod no longer requires go-bip39. go mod tidy keeps its two go.sum
lines, because a test in sneak/secret's bip85 package imports it, and
drops six lines that only go-bip39's own requirements needed.

Model: opus-5-5

README.md

@@ -6,7 +6,7 @@ identities and child mnemonics, each of which can be recreated from that
 mnemonic at any time. The same mnemonic, key type and index always give the same
 key.
 
-It uses the BIP-85 entropy deriver from `sneak.berlin/go/secret/pkg/bip85` and
+It uses the BIP-85 entropy deriver from `git.eeqj.de/sneak/secret/pkg/bip85` and
 takes the same steps as that repository's `agehd` package.
 
 Commands are grouped by what is derived: `keyfunc ssh ...` for ed25519 SSH keys,

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 (

go.sum

@@ -4,6 +4,8 @@ filippo.io/age v1.3.2 h1:r6RSZLFSMm6rzKepZ7ZAYkKCu14f3/Me8c7uKYh7C8c=
 filippo.io/age v1.3.2/go.mod h1:TH/Yr2sSRhCKbaH4XPxpUV0Us8Gv6txYUpiZQWz8Evk=
 filippo.io/hpke v0.4.0 h1:p575VVQ6ted4pL+it6M00V/f2qTZITO0zgmdKCkd5+A=
 filippo.io/hpke v0.4.0/go.mod h1:EmAN849/P3qdeK+PCMkDpDm83vRHM5cDipBJ8xbQLVY=
+git.eeqj.de/sneak/secret v0.0.0-20260810132333-41cea400a7fd h1:6YFV6horz2wDFPWWhour8qx8gLGyO0qoplwEeOuQ2J4=
+git.eeqj.de/sneak/secret v0.0.0-20260810132333-41cea400a7fd/go.mod h1:gKCcMZvlBOqusn/BxR8IyFmSJQr6R4vvjJ926iNpOSI=
 github.com/btcsuite/btcd v0.25.0 h1:JPbjwvHGpSywBRuorFFqTjaVP4y6Qw69XJ1nQ6MyWJM=
 github.com/btcsuite/btcd v0.25.0/go.mod h1:qbPE+pEiR9643E1s1xu57awsRhlCIm1ZIi6FfeRA4KE=
 github.com/btcsuite/btcd/btcec/v2 v2.5.0 h1:KioMXOWa76b86sTZZOmbzv/ldaQCmB8KFAyn5PbB8E8=
@@ -28,6 +30,8 @@ github.com/spf13/pflag v1.0.9 h1:9exaQaMOCwffKiiiYk6/BndUBv+iRViNW+4lEMi0PvY=
 github.com/spf13/pflag v1.0.9/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/stretchr/testify v1.12.1 h1:EuwCh5fleGS7H32xRwO3wRGT7DxrDhLAT6FF8MpWDWE=
 github.com/stretchr/testify v1.12.1/go.mod h1:MDEgiDPPsNp5cuIrHPPCyornHKgEVbtFUmoNlxoYthg=
+github.com/tyler-smith/go-bip39 v1.1.0 h1:5eUemwrMargf3BSLRRCalXT93Ns6pQJIjYQN2nyfOP8=
+github.com/tyler-smith/go-bip39 v1.1.0/go.mod h1:gUYDtqQw1JS3ZJ8UWVcGTGqqr6YIN3CWg+kkNaLt55U=
 go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=
 go.yaml.in/yaml/v3 v3.0.5 h1:N6y/pJk8buWs9NY5ERU2HSMfm+IuD/OtfdAnq6kESPw=
 go.yaml.in/yaml/v3 v3.0.5/go.mod h1:HVTZu1O7/Vkt2N+BFy8Zza+lnLsABggaTM2ZpNIGuKg=
@@ -38,5 +42,3 @@ golang.org/x/sys v0.48.0/go.mod h1:hNLxWAXmnKAxqDtdwIYC4bM9oQPEecfsnNMuSxOs3og=
 golang.org/x/term v0.46.0 h1:3+OXuTbaKDgwk8jTi3aSLHRlmWqHEUDUtxnbFigO4YE=
 golang.org/x/term v0.46.0/go.mod h1:+K02xbkittuwc0Am4abfA3Fc+XRGXkvBXNO88NCXPoc=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-sneak.berlin/go/secret v0.0.0-20261007105610-ef0ae90768c8 h1:Bd2bUsRCN8xhcrpH3LpJqHxR2QffeOuF5z76iP4BFnw=
-sneak.berlin/go/secret v0.0.0-20261007105610-ef0ae90768c8/go.mod h1:uVx9ZuE7ZMIOBY2B1ElXCs97CTsEfuham3NQRdLj5lI=

internal/childmnemonic/childmnemonic.go

@@ -5,10 +5,10 @@ import (
 	"errors"
 	"fmt"
 
+	"git.eeqj.de/sneak/secret/pkg/bip85"
 	"github.com/btcsuite/btcd/btcutil/hdkeychain"
 	"sneak.berlin/go/keyfunc/internal/bip39"
 	"sneak.berlin/go/keyfunc/internal/derive"
-	"sneak.berlin/go/secret/pkg/bip85"
 )
 
 // english is the number BIP-85 gives the English word list.

internal/derive/derive.go

@@ -5,10 +5,10 @@ import (
 	"errors"
 	"fmt"
 
+	"git.eeqj.de/sneak/secret/pkg/bip85"
 	"github.com/btcsuite/btcd/btcutil/hdkeychain"
 	"github.com/btcsuite/btcd/chaincfg"
 	"sneak.berlin/go/keyfunc/internal/bip39"
-	"sneak.berlin/go/secret/pkg/bip85"
 )
 
 const (