swaps: add type hints to gui swap suggestion flow

diff --git a/electrum/gui/qt/main_window.py b/electrum/gui/qt/main_window.py
index a2aaf6a..927e682 100644
--- a/electrum/gui/qt/main_window.py
+++ b/electrum/gui/qt/main_window.py
@@ -107,6 +107,7 @@ from electrum.gui.common_qt.util import TaskThread
 if TYPE_CHECKING:
     from . import ElectrumGui
     from electrum.submarine_swaps import SwapOffer
+    from electrum.lnchannel import Channel
 
 
 class StatusBarButton(QToolButton):
@@ -1258,32 +1259,43 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger, QtEventListener):
     def protect(self, func, args, password):
         return func(*args, password)
 
-    def run_swap_dialog(self, is_reverse=None, recv_amount_sat=None, channels=None):
+    def run_swap_dialog(
+        self,
+        is_reverse: Optional[bool] = None,
+        recv_amount_sat_or_max: Optional[Union[int, str]] = None,
+        channels: Optional[Sequence['Channel']] = None,
+    ) -> bool:
         if not self.network:
             self.show_error(_("You are offline."))
-            return
+            return False
         if not self.wallet.lnworker:
             self.show_error(_('Lightning is disabled'))
-            return
+            return False
         if not self.wallet.lnworker.num_sats_can_send() and not self.wallet.lnworker.num_sats_can_receive():
             self.show_error(_("You do not have liquidity in your active channels."))
-            return
+            return False
 
         transport = self.create_sm_transport()
         if not transport:
-            return
+            return False
 
         with transport:
             if not self.initialize_swap_manager(transport):
-                return
-            d = SwapDialog(self, transport, is_reverse=is_reverse, recv_amount_sat=recv_amount_sat, channels=channels)
+                return False
+            d = SwapDialog(
+                self,
+                transport,
+                is_reverse=is_reverse,
+                recv_amount_sat_or_max=recv_amount_sat_or_max,
+                channels=channels
+            )
             try:
                 return d.run(transport)
             except InvalidSwapParameters as e:
                 self.show_error(str(e))
-                return
+                return False
             except UserCancelled:
-                return
+                return False
 
     def create_sm_transport(self) -> Optional['SwapServerTransport']:
         sm = self.wallet.lnworker.swap_manager
diff --git a/electrum/gui/qt/receive_tab.py b/electrum/gui/qt/receive_tab.py
index 39ec97d..74377b3 100644
--- a/electrum/gui/qt/receive_tab.py
+++ b/electrum/gui/qt/receive_tab.py
@@ -112,7 +112,7 @@ class ReceiveTab(QWidget, MessageBoxMixin, Logger):
         def on_receive_swap():
             if self.receive_swap_button.suggestion:
                 chan, swap_recv_amount_sat = self.receive_swap_button.suggestion
-                self.window.run_swap_dialog(is_reverse=True, recv_amount_sat=swap_recv_amount_sat, channels=[chan])
+                self.window.run_swap_dialog(is_reverse=True, recv_amount_sat_or_max=swap_recv_amount_sat, channels=[chan])
         self.receive_swap_button.clicked.connect(on_receive_swap)
         buttons = QHBoxLayout()
         buttons.addWidget(self.receive_rebalance_button)
diff --git a/electrum/gui/qt/send_tab.py b/electrum/gui/qt/send_tab.py
index 1550e85..474cbe4 100644
--- a/electrum/gui/qt/send_tab.py
+++ b/electrum/gui/qt/send_tab.py
@@ -712,7 +712,7 @@ class SendTab(QWidget, MessageBoxMixin, Logger):
                     self.window.new_channel_dialog(amount_sat=amount_sat, min_amount_sat=min_amount_sat)
                 elif r == 'swap':
                     chan, swap_recv_amount_sat = can_pay_with_swap
-                    self.window.run_swap_dialog(is_reverse=False, recv_amount_sat=swap_recv_amount_sat, channels=[chan])
+                    self.window.run_swap_dialog(is_reverse=False, recv_amount_sat_or_max=swap_recv_amount_sat, channels=[chan])
                 elif r == 'onchain':
                     self.pay_onchain_dialog(invoice.get_outputs(), nonlocal_only=True, invoice=invoice)
             return
diff --git a/electrum/gui/qt/swap_dialog.py b/electrum/gui/qt/swap_dialog.py
index 49680a4..73a003c 100644
--- a/electrum/gui/qt/swap_dialog.py
+++ b/electrum/gui/qt/swap_dialog.py
@@ -27,6 +27,7 @@ from .my_treeview import create_toolbar_with_menu, MyTreeView
 if TYPE_CHECKING:
     from .main_window import ElectrumWindow
     from electrum.submarine_swaps import SwapServerTransport, SwapOffer
+    from electrum.lnchannel import Channel
 
 CANNOT_RECEIVE_WARNING = _(
 """The requested amount is higher than what you can receive in your currently open channels.
@@ -43,7 +44,14 @@ class InvalidSwapParameters(Exception): pass
 
 class SwapDialog(WindowModalDialog, QtEventListener):
 
-    def __init__(self, window: 'ElectrumWindow', transport: 'SwapServerTransport', is_reverse=None, recv_amount_sat=None, channels=None):
+    def __init__(
+        self,
+        window: 'ElectrumWindow',
+        transport: 'SwapServerTransport',
+        is_reverse: Optional[bool] = None,
+        recv_amount_sat_or_max: Optional[Union[int, str]] = None,  # sat or '!'
+        channels: Optional[Sequence['Channel']] = None,
+    ):
         WindowModalDialog.__init__(self, window, _('Submarine Swap'))
         self.window = window
         self.config = window.config
@@ -120,8 +128,9 @@ class SwapDialog(WindowModalDialog, QtEventListener):
         buttons = Buttons(CancelButton(self), self.ok_button)
         vbox.addLayout(buttons)
         buttons.insertWidget(0, self.server_button)
-        if recv_amount_sat:
-            self.init_recv_amount(recv_amount_sat)
+        if recv_amount_sat_or_max:
+            assert isinstance(recv_amount_sat_or_max, (int, str)), f"invalid {type(recv_amount_sat_or_max)=}"
+            self.init_recv_amount(recv_amount_sat_or_max)
         self.update()
         self.needs_tx_update = True
 
@@ -321,15 +330,15 @@ class SwapDialog(WindowModalDialog, QtEventListener):
         self.fee_label.setText(fee_text)
         self.fee_label.repaint()  # macOS hack for #6269
 
-    def run(self, transport):
+    def run(self, transport: 'SwapServerTransport') -> bool:
         """Can raise InvalidSwapParameters."""
         if not self.exec():
-            return
+            return False
         if self.is_reverse:
             lightning_amount = self.send_amount_e.get_amount()
             onchain_amount = self.recv_amount_e.get_amount()
             if lightning_amount is None or onchain_amount is None:
-                return
+                return False
             sm = self.swap_manager
             coro = sm.reverse_swap(
                 transport=transport,
@@ -342,17 +351,17 @@ class SwapDialog(WindowModalDialog, QtEventListener):
                 funding_txid = self.window.run_coroutine_dialog(coro, _('Initiating swap...'))
             except Exception as e:
                 self.window.show_error(f"Reverse swap failed: {str(e)}")
-                return
+                return False
             self.window.on_swap_result(funding_txid, is_reverse=True)
             return True
         else:
             lightning_amount = self.recv_amount_e.get_amount()
             onchain_amount = self.send_amount_e.get_amount()
             if lightning_amount is None or onchain_amount is None:
-                return
+                return False
             if lightning_amount > self.lnworker.num_sats_can_receive():
                 if not self.window.question(CANNOT_RECEIVE_WARNING):
-                    return
+                    return False
             self.window.protect(self.do_normal_swap, (transport, lightning_amount, onchain_amount))
             return True
 
diff --git a/electrum/gui/qt/utxo_list.py b/electrum/gui/qt/utxo_list.py
index 6be01fb..4e6de35 100644
--- a/electrum/gui/qt/utxo_list.py
+++ b/electrum/gui/qt/utxo_list.py
@@ -255,7 +255,7 @@ class UTXOList(MyTreeView):
     def swap_coins(self, coins):
         #self.clear_coincontrol()
         self.add_to_coincontrol(coins)
-        self.main_window.run_swap_dialog(is_reverse=False, recv_amount_sat='!')
+        self.main_window.run_swap_dialog(is_reverse=False, recv_amount_sat_or_max='!')
         self.clear_coincontrol()
 
     def can_open_channel(self, coins):
diff --git a/electrum/lnworker.py b/electrum/lnworker.py
index bdf96e5..18abdd9 100644
--- a/electrum/lnworker.py
+++ b/electrum/lnworker.py
@@ -2925,10 +2925,10 @@ class LNWallet(LNWorker):
                 # add safety margin
                 delta += delta // 100 + 1
                 if func(deltas={chan:delta}) >= amount_sat:
-                    suggestions.append((chan, delta))
+                    suggestions.append((chan, int(delta)))
                 elif direction == RECEIVED and func(deltas={chan:2*delta}) >= amount_sat:
                     # MPP heuristics has a 0.5 slope
-                    suggestions.append((chan, 2*delta))
+                    suggestions.append((chan, int(2*delta)))
         if not suggestions:
             raise NotEnoughFunds
         return suggestions
@@ -3002,7 +3002,7 @@ class LNWallet(LNWorker):
             return chan, swap_recv_amount
         return None
 
-    def suggest_swap_to_receive(self, amount_sat):
+    def suggest_swap_to_receive(self, amount_sat: int):
         assert amount_sat > self.num_sats_can_receive(), f"{amount_sat=} | {self.num_sats_can_receive()=}"
         try:
             suggestions = self._suggest_channels_for_rebalance(RECEIVED, amount_sat)