Fix Windows VT EOL wrap by syncing real console cursor

Windows VT terminals do not consistently wrap the cursor when a line
exactly fills the terminal width.
Previously we assumed a wrap always happened, which could desynchronize
the logical cursor from the real console cursor and break subsequent
cursor movement.
This change queries the real cursor position and updates posxy
accordingly, and adds regression tests for both wrap and no-wrap cases.

Signed-off-by: Yongtao Huang <yongtaoh2022@gmail.com>

Author: hyongtao-code

Lib/_pyrepl/windows_console.py

@@ -272,9 +272,22 @@ def __write_changed_line(
 
         self.__write(newline[x_pos:])
         if wlen(newline) == self.width:
-            # If we wrapped we want to start at the next line
-            self._move_relative(0, y + 1)
-            self.posxy = 0, y + 1
+            if self.__vt_support:
+                info = CONSOLE_SCREEN_BUFFER_INFO()
+                if not GetConsoleScreenBufferInfo(OutHandle, info):
+                    raise WinError(GetLastError())
+                win_y = int(info.dwCursorPosition.Y - info.srWindow.Top)
+                expected = y - self.__offset
+                if win_y == expected + 1:
+                    # Terminal wrapped to next row.
+                    self.posxy = 0, y + 1
+                else:
+                    # Terminal did not wrap; cursor stays at end-of-line.
+                    self.posxy = self.width, y
+            else:
+                # If we wrapped we want to start at the next line
+                self._move_relative(0, y + 1)
+                self.posxy = 0, y + 1
         else:
             self.posxy = wlen(newline), y