coldcard: disable test_signtx

```
ERROR: coldcard: test_signtx (test_device.TestSignTx.test_signtx) (addrtypes=['legacy'], multisig_types=['legacy'], external=True, op_return=False)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/__w/HWI/HWI/test/test_device.py", line 588, in test_signtx
    self._test_signtx(addrtypes, multisig_types, external, op_return)
  File "/__w/HWI/HWI/test/test_device.py", line 576, in _test_signtx
    self._generate_and_finalize(True, psbt)
  File "/__w/HWI/HWI/test/test_device.py", line 403, in _generate_and_finalize
    self.assertTrue(first_sign_res["signed"])
                    ~~~~~~~~~~~~~~^^^^^^^^^^
KeyError: 'signed'
```

Author: Sjors

test/test_device.py

@@ -137,7 +137,7 @@ def create(*args, **kwargs):
         return c
 
 class DeviceTestCase(unittest.TestCase):
-    def __init__(self, bitcoind, emulator=None, interface='library', methodName='runTest'):
+    def __init__(self, bitcoind, emulator: DeviceEmulator = None, interface='library', methodName='runTest'):
         super(DeviceTestCase, self).__init__(methodName)
         self.bitcoind = bitcoind
         self.rpc = bitcoind.rpc
@@ -582,6 +582,9 @@ def _test_signtx(self, input_types, multisig_types, external, op_return: bool):
 
     # Test wrapper to avoid mixed-inputs signing for Ledger
     def test_signtx(self):
+        if self.emulator.type == "coldcard":
+            # https://github.com/bitcoin-core/HWI/pull/795#issuecomment-3112271927
+            raise unittest.SkipTest("Coldcard sign test temporarily disabled")
 
         for addrtypes, multisig_types, external, op_return in self.signtx_cases:
             with self.subTest(addrtypes=addrtypes, multisig_types=multisig_types, external=external, op_return=op_return):