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/modules/friend_of.ludic

@@ -5,8 +5,8 @@
 import "bank"
 program FriendOf {
   friend module lab of bank
-  entry (bank_st: mut BankState) {
-    add(bank_st, 7)
-    print(`{bank_st.balance} {total(bank_st)}`)
+  entry {
+    add(7)
+    print(`{balance} {total()}`)
   }
 }