fix(window): stop forcing maximised on a window the user left normal

The previous version over-corrected: a normal window came back maximised
after Win+D. Two causes, both fixed.

- It read FMX's WindowState, which does not reliably follow a native
  un-maximise, so FWantMaximized never cleared. Now reads Win32 IsZoomed /
  IsIconic, which is the actual truth.
- The restore fires its own resize, reporting whatever FMX decided — recording
  that erased the very intent we were preserving. FWasMinimized now gates the
  restore's resize out of the tracking.

Activate then corrects both directions: re-maximise when FMX dropped a
maximised window, restore when Windows brought a normal one back maximised.
Degrades safely — if the minimise resize never fires, it simply does nothing.

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

delphi-backend/UMainForm.pas

@@ -79,6 +79,9 @@ type
     // which happens however the user comes back. FWantMaximized mirrors the
     // user's LAST deliberate choice, so we never fight a normal-size window.
     FWantMaximized: Boolean;
+    // True between an external minimise and the following activate, so the
+    // restore's own resize is not mistaken for a user resize.
+    FWasMinimized: Boolean;
     FServer: TPMHTTPServer;
     FBridge: TPMBridge;
     // Accumulates base64 chunks for large file saves (attachments too big
@@ -174,6 +177,7 @@ begin
   // The .fmx ships WindowState = wsMaximized, so that is the starting intent.
   // Wired here (not in the .fmx) to keep the designer file untouched.
   FWantMaximized := (WindowState = TWindowState.wsMaximized);
+  FWasMinimized  := False;
   OnResize   := FormResizeTrackState;
   OnActivate := FormActivateRestoreState;
 
@@ -1503,23 +1507,44 @@ begin
   Application.Terminate;
 end;
 
-// Remember the window state the USER settled on. Minimised is skipped on
-// purpose: that is precisely the state we have to survive, not record.
+// Remember the state the USER settled on. Reads Win32 (IsZoomed/IsIconic)
+// rather than FMX's WindowState, which does not reliably follow a native
+// un-maximise — that is why the first version never cleared the flag.
+//
+// The restore itself fires a resize too, and that one must NOT be recorded:
+// it reports whatever FMX decided (often "normal"), which would erase the
+// intent we are trying to preserve. FWasMinimized gates it out.
 procedure TMainForm.FormResizeTrackState(Sender: TObject);
+var
+  LHwnd: HWND;
 begin
-  if WindowState = TWindowState.wsMaximized then
-    FWantMaximized := True
-  else if WindowState = TWindowState.wsNormal then
-    FWantMaximized := False;
+  LHwnd := WindowHandleToPlatform(Self.Handle).Wnd;
+  if LHwnd = 0 then Exit;
+  if IsIconic(LHwnd) then
+  begin
+    FWasMinimized := True;   // the state we must survive, not record
+    Exit;
+  end;
+  if FWasMinimized then Exit;         // this resize IS the restore
+  FWantMaximized := IsZoomed(LHwnd);  // genuine user-driven resize
 end;
 
-// Re-apply "maximised" when the window comes back from an external minimise.
-// Runs however the user returns (taskbar, tray, Alt+Tab), because none of our
-// own restore paths are involved in a plain taskbar click.
+// Re-apply the remembered state once the window is back. Runs however the
+// user returns (taskbar, tray, Alt+Tab) — a plain taskbar restore never goes
+// through any of our own restore paths. Corrects BOTH directions: FMX drops
+// a maximised window to normal, and Windows can restore a normal window
+// maximised.
 procedure TMainForm.FormActivateRestoreState(Sender: TObject);
+var
+  LHwnd: HWND;
 begin
-  if FWantMaximized and (WindowState = TWindowState.wsNormal) then
-    WindowState := TWindowState.wsMaximized;
+  if not FWasMinimized then Exit;
+  LHwnd := WindowHandleToPlatform(Self.Handle).Wnd;
+  if (LHwnd = 0) or IsIconic(LHwnd) then Exit;
+  FWasMinimized := False;
+  if FWantMaximized = IsZoomed(LHwnd) then Exit;   // already right
+  if FWantMaximized then ShowWindow(LHwnd, SW_SHOWMAXIMIZED)
+  else                   ShowWindow(LHwnd, SW_RESTORE);
 end;
 
 procedure TMainForm.AutofillTimerTick(Sender: TObject);