trezor: don't try to sign non-ismine inputs

progress towards coinjoin

related https://github.com/spesmilo/electrum/issues/8868

electrum/plugins/trezor/trezor.py

@@ -352,7 +352,7 @@ class TrezorPlugin(HW_PluginBase):
                     assert isinstance(tx, PartialTransaction)
                     assert isinstance(txin, PartialTxInput)
                     assert keystore
-                    if txin.is_complete():
+                    if txin.is_complete() or not txin.is_mine:
                         txinputtype.script_type = InputScriptType.EXTERNAL
                         assert txin.scriptpubkey
                         txinputtype.script_pubkey = txin.scriptpubkey

electrum/transaction.py

@@ -1389,6 +1389,7 @@ class PartialTxInput(TxInput, PSBTSection):
         self._unknown = {}  # type: Dict[bytes, bytes]
 
         self._script_descriptor = None  # type: Optional[Descriptor]
+        self.is_mine = False  # type: bool  # whether the wallet considers the input to be ismine
         self._trusted_value_sats = None  # type: Optional[int]
         self._trusted_address = None  # type: Optional[str]
         self._is_p2sh_segwit = None  # type: Optional[bool]  # None means unknown

electrum/wallet.py

@@ -2443,6 +2443,7 @@ class Abstract_Wallet(ABC, Logger, EventListener):
                 self.lnworker.swap_manager.add_txin_info(txin)
             return
         txin.script_descriptor = self.get_script_descriptor_for_address(address)
+        txin.is_mine = True
         self._add_txinout_derivation_info(txin, address, only_der_suffix=only_der_suffix)
         txin.block_height = self.adb.get_tx_height(txin.prevout.txid.hex()).height