fix: resolve exported type stuttering issues (revive)

- Rename VaultMetadata to Metadata in internal/vault package to avoid stuttering
- Rename BIP85DRNG to DRNG in pkg/bip85 package to avoid stuttering
- Update all references in code and tests

pkg/bip85/bip85.go

@@ -45,29 +45,29 @@ var (
 	TestNetPrivateKey = []byte{0x04, 0x35, 0x83, 0x94}
 )
 
-// BIP85DRNG is a deterministic random number generator seeded by BIP85 entropy
-type BIP85DRNG struct {
+// DRNG is a deterministic random number generator seeded by BIP85 entropy
+type DRNG struct {
 	shake io.Reader
 }
 
 // NewBIP85DRNG creates a new DRNG seeded with BIP85 entropy
-func NewBIP85DRNG(entropy []byte) *BIP85DRNG {
+func NewBIP85DRNG(entropy []byte) *DRNG {
 	// The entropy must be exactly 64 bytes (512 bits)
 	if len(entropy) != 64 {
-		panic("BIP85DRNG entropy must be 64 bytes")
+		panic("DRNG entropy must be 64 bytes")
 	}
 
 	// Initialize SHAKE256 with the entropy
 	shake := sha3.NewShake256()
 	shake.Write(entropy)
 
-	return &BIP85DRNG{
+	return &DRNG{
 		shake: shake,
 	}
 }
 
 // Read implements the io.Reader interface
-func (d *BIP85DRNG) Read(p []byte) (n int, err error) {
+func (d *DRNG) Read(p []byte) (n int, err error) {
 	return d.shake.Read(p)
 }
 
@@ -266,6 +266,7 @@ func DeriveXPRV(masterKey *hdkeychain.ExtendedKey, index uint32) (*hdkeychain.Ex
 func doubleSHA256(data []byte) []byte {
 	hash1 := sha256.Sum256(data)
 	hash2 := sha256.Sum256(hash1[:])
+
 	return hash2[:]
 }