Prevent cursor repositioning during mouse selection (#19182)

- Modify the cursor repositioning logic to check if a selection is in
progress
- Only reposition the cursor when the mouse is used for positioning, not
during selection operations

Closes #19181

(cherry picked from commit 88ab154)
Service-Card-Id: PVTI_lADOAF3p4s4AxadtzgdSbu4
Service-Version: 1.23

Author: MengAiDev

src/cascadia/TerminalControl/ControlCore.cpp

@@ -2064,7 +2064,7 @@ namespace winrt::Microsoft::Terminal::Control::implementation
             _terminal->MultiClickSelection(terminalPosition, mode);
             selectionNeedsToBeCopied = true;
         }
-        else if (_settings->RepositionCursorWithMouse()) // This is also mode==Char && !shiftEnabled
+        else if (_settings->RepositionCursorWithMouse() && !selectionNeedsToBeCopied) // Don't reposition cursor if this is part of a selection operation
         {
             _repositionCursorWithMouse(terminalPosition);
         }