fix(examples): restart ball ids when the scene is cleared

World_Reset kept counting, so after one reset the ball dropped from
60 m was ball 10, not the ball 5 the plain build's output and the log
from before the reset name. The agent in the first check noticed and
worked around it. Clear now restarts ids at 1, so Reset brings back
balls 1 to 5.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

examples/Basic/implementations/Basic.World.cpp

@@ -16,6 +16,7 @@ void Basic::World::Reset() {
 
 void Basic::World::Clear() {
     balls.clear();
+    nextId = 1;
     time = 0;
     fastest = 0;
 }