feat(autofill): "Clear the field before typing" setting (default ON)

The Ctrl+A + Del sent before each field misbehaves on targets where Ctrl+A
isn't select-all (terminals, some remote desktops). New synced setting
(autofillClearField, Settings > Autofill) gates it: JS appends clear=0 to
cmd://autofill/execute when off; ExecuteAutofill wraps the three
SendSelectAllAndDelete calls behind AClearFirst. Absent param = ON, so
existing behavior is unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

delphi-backend/UMainForm.pas

@@ -105,6 +105,9 @@ type
     // True when the pending autofill should type ONLY the username (quick
     // search "autofill username" — right-click / Shift+Enter in fill mode).
     FAutofillPendingUserOnly: Boolean;
+    // Send Ctrl+A + Del before typing each field (user setting, default ON;
+    // OFF for targets where Ctrl+A isn't select-all — terminals, RDP).
+    FAutofillPendingClear: Boolean;
     // Created dynamically in FormCreate so the directive can pick either
     // TTMSFNCWebBrowser or TTMSFNCEdgeWebBrowser at compile time without
     // needing two .fmx variants. Aligned to Client to fill the remaining
@@ -897,6 +900,7 @@ begin
     FAutofillPendingHWND := FAutofillTargetHWND;
     FAutofillPendingHide := GetParam('hide_after') = '1';
     FAutofillPendingUserOnly := GetParam('field') = 'user';
+    FAutofillPendingClear := GetParam('clear') <> '0';   // absent = ON
     FAutofillTargetHWND := 0;
 
     // Small timer so SetForegroundWindow has time to take effect before
@@ -1449,7 +1453,7 @@ procedure TMainForm.AutofillTimerTick(Sender: TObject);
 var
   TargetHwnd: HWND;
   PendingUser, PendingPass: string;
-  HideAfter, UserOnly: Boolean;
+  HideAfter, UserOnly, ClearFirst: Boolean;
   ForegroundAfter: HWND;
 begin
   TargetHwnd  := FAutofillPendingHWND;
@@ -1457,11 +1461,13 @@ begin
   PendingPass := FAutofillPendingPass;
   HideAfter   := FAutofillPendingHide;
   UserOnly    := FAutofillPendingUserOnly;
+  ClearFirst  := FAutofillPendingClear;
   FAutofillPendingHWND := 0;
   FAutofillPendingUser := '';
   FAutofillPendingPass := '';
   FAutofillPendingHide := False;
   FAutofillPendingUserOnly := False;
+  FAutofillPendingClear := False;
 
   TTimer(Sender).Enabled := False;
   TTimer(Sender).Free;
@@ -1470,7 +1476,7 @@ begin
   // (quick-search beside the target), it stays visible during the fill; if it
   // started hidden, the MinimizeToTray below re-hides it anyway.
   var LFillOk := FBridge.ExecuteAutofill(TargetHwnd, PendingUser, PendingPass,
-    UserOnly, not HideAfter);
+    UserOnly, not HideAfter, ClearFirst);
   ForegroundAfter := GetForegroundWindow;
   LogLine(Format('Autofill executed — target=%s, foreground_after=%s, ok=%s',
     [IntToHex(TargetHwnd, 8), IntToHex(ForegroundAfter, 8),