Timer refactor: stopwatch-like semantics, mcrfpy.timers collection closes #173

Major Timer API improvements:
- Add `stopped` flag to Timer C++ class for proper state management
- Add `start()` method to restart stopped timers (preserves callback)
- Add `stop()` method that removes from engine but preserves callback
- Make `active` property read-write (True=start/resume, False=pause)
- Add `start=True` init parameter to create timers in stopped state
- Add `mcrfpy.timers` module-level collection (tuple of active timers)
- One-shot timers now set stopped=true instead of clearing callback
- Remove deprecated `setTimer()` and `delTimer()` module functions

Timer callbacks now receive (timer, runtime) instead of just (runtime).
Updated all tests to use new Timer API and callback signature.

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/unit/test_grid_cell_events.py

@@ -68,9 +68,7 @@ def test_cell_hover():
     automation.moveTo(150, 150)
     automation.moveTo(200, 200)
 
-    def check_hover(runtime):
-        mcrfpy.delTimer("check_hover")
-
+    def check_hover(timer, runtime):
         print(f"  Enter events: {len(enter_events)}, Exit events: {len(exit_events)}")
         print(f"  Hovered cell: {grid.hovered_cell}")
 
@@ -82,7 +80,7 @@ def test_cell_hover():
         # Continue to click test
         test_cell_click()
 
-    mcrfpy.setTimer("check_hover", check_hover, 200)
+    mcrfpy.Timer("check_hover", check_hover, 200, once=True)
 
 
 def test_cell_click():
@@ -105,9 +103,7 @@ def test_cell_click():
 
     automation.click(200, 200)
 
-    def check_click(runtime):
-        mcrfpy.delTimer("check_click")
-
+    def check_click(timer, runtime):
         print(f"  Click events: {len(click_events)}")
 
         if len(click_events) >= 1:
@@ -118,7 +114,7 @@ def test_cell_click():
         print("\n=== All grid cell event tests passed! ===")
         sys.exit(0)
 
-    mcrfpy.setTimer("check_click", check_click, 200)
+    mcrfpy.Timer("check_click", check_click, 200, once=True)
 
 
 if __name__ == "__main__":