Use "Take One" for digital watch.

examples/digitalwatch/model_digitalwatch.xml

@@ -2,7 +2,7 @@
   <delta>1 ms</delta>
 
   <statechart>
-    <semantics big_step_maximality="take_many"/>
+    <semantics big_step_maximality="take_one"/>
 
     <inport name="in">
       <event name="bottomLeftPressed"/>

src/sccd/realtime/time.py

@@ -44,8 +44,8 @@ class Timer:
         self.paused_at = self.now()
         self.paused = True
 
-    # Only call when not paused!
     def now(self) -> int:
+        assert not self.paused
         return self.convert(self.impl.get_time()) - self.started_at
 
     def is_paused(self):