fix: Update cpython submodule to v3.14.0 and fix flaky tests

- Update cpython submodule from v3.12.2 to v3.14.0
- Fix test_timer_object.py: Add delTimer call to prevent double-cancel
- Fix test_viewport_scaling.py: Handle headless mode for window resize

Test suite now achieves 100% pass rate (129/129 tests).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tests/unit/test_timer_object.py

@@ -68,10 +68,11 @@ def run_tests(runtime):
     
     # Cancel after 350ms (should fire once)
     def cancel_timer3(runtime):
+        mcrfpy.delTimer("cancel_timer3")  # Make this a one-shot timer
         print("  Canceling timer3...")
         timer3.cancel()
         print("  Timer3 canceled")
-    
+
     mcrfpy.setTimer("cancel_timer3", cancel_timer3, 350)
     
     # Test 4: Test interval modification