wip(0.S2): migrate - a var nothing writes becomes a let; a state is keyed by its module, directory or program, so every program's plan agrees; paths normalized; program states named SceneDemoState / scene_demo_st; the LSP reads state, mut and entry/handler parameters

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

examples/events/recurse.ludic

@@ -6,18 +6,16 @@
 #
 # Running it prints:  16   (the cycle bottoms out at the depth cap, deterministically)
 program Recurse {
-  state RecurseState {
-    n: int = 0
-  }
+  var n: int = 0
 
   event Ping { }
   event Pong { }
 
-  @On(Ping) handler A(recurse_st: mut RecurseState) { recurse_st.n += 1; emit Pong() }   # each Ping deepens by one Pong
+  @On(Ping) handler A { n += 1; emit Pong() }   # each Ping deepens by one Pong
   @On(Pong) handler B { emit Ping() }              # ...and each Pong by one Ping
 
-  entry (recurse_st: RecurseState) {
+  entry {
     emit Ping()
-    print(recurse_st.n)
+    print(n)
   }
 }