fix(protocol-kit): handle CONTRACT_SIGNATURE in toSafeTransactionType

`toSafeTransactionType` creates `EthSafeSignature` with
`isContractSignature=false` for all confirmations, including
CONTRACT_SIGNATURE types from the Safe Transaction Service.

This causes `buildSignatureBytes` to concatenate the full stored
signature blob (r+s+v+dynamic data) as-is instead of properly
splitting it into static part (r, s=offset, v=0) and dynamic part
(length + inner data). For multi-owner Safes, this breaks the
combined signatures layout — the second signer's 65-byte constant
part overlaps with the first signer's dynamic data, causing
GS021 ("Invalid contract signature provided") on execution.

The fix detects CONTRACT_SIGNATURE confirmations and:
1. Extracts the inner signature data from the stored format
   using the s offset (which points to the length-prefixed data)
2. Creates EthSafeSignature with isContractSignature=true
3. This lets buildSignatureBytes properly compute dynamic offsets

Affects any Safe with EIP-1271 contract signature owners (passkey
signers via SafeWebAuthnSignerProxy, nested Safes, etc.) when
executing transactions that include contract signature confirmations
fetched from the Safe Transaction Service.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: barraguda

packages/protocol-kit/src/Safe.ts

@@ -1287,8 +1287,22 @@ class Safe {
     })
     serviceTransactionResponse.confirmations?.map(
       (confirmation: SafeMultisigConfirmationResponse) => {
-        const signature = new EthSafeSignature(confirmation.owner, confirmation.signature)
-        safeTransaction.addSignature(signature)
+        if (confirmation.signatureType === 'CONTRACT_SIGNATURE') {
+          // Contract signatures are stored as: r(32) + s(32) + v(1) + dataLen(32) + data(N)
+          // Extract just the inner signature data that isValidSignature expects.
+          const sig = confirmation.signature.startsWith('0x')
+            ? confirmation.signature.slice(2)
+            : confirmation.signature
+          // Read s (bytes 32-63) to find the byte offset to the length-prefixed data
+          const s = parseInt(sig.slice(64, 128), 16)
+          const dataLen = parseInt(sig.slice(s * 2, s * 2 + 64), 16)
+          const innerData = '0x' + sig.slice(s * 2 + 64, s * 2 + 64 + dataLen * 2)
+          const signature = new EthSafeSignature(confirmation.owner, innerData, true)
+          safeTransaction.addSignature(signature)
+        } else {
+          const signature = new EthSafeSignature(confirmation.owner, confirmation.signature)
+          safeTransaction.addSignature(signature)
+        }
       }
     )
     return safeTransaction