fix(fwt): fix vlq max length calculation

The VLQ max length calculation was incorrect, leading to
insufficient buffer allocation for the token. This commit
corrects the calculation and updates the tests to include
a test case for max-uint64.

Author: DeltaLaboratory

fwt.go

@@ -133,7 +133,7 @@ func (s *Signer) Sign(data any) (string, error) {
 	}
 
 	// allocate token type + VLQ Max Length + marshaled length + signature length
-	token := memory.Alloc(1 + 9 + len(marshaled) + len(signature))
+	token := memory.Alloc(1 + 10 + len(marshaled) + len(signature))
 	token[0] = byte(s.signatureType)
 
 	vlqLength, err := encodeVLQ(token[1:], uint64(len(marshaled)))

vlq_test.go

@@ -24,6 +24,7 @@ func TestVLQEncodeDecode(t *testing.T) {
 		{"two-bytes-max", 16384, 2, false, 2},
 		{"large-value", 1234567890, 5, false, 5},
 		{"max-uint32", uint64(^uint32(0)), 5, false, 5},
+		{"max-uint64", ^uint64(0), 10, false, 10},
 	}
 
 	for _, tt := range tests {