wip(0.S1, 0.S2): state records, mut and read-only state parameters, entry injection, module var refused; ludic migrate state

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

examples/rejected/module_let_write.ludic

@@ -0,0 +1,8 @@
+# 0.S: a module-level let is immutable all the way down - a write through it is refused
+program ModuleLetWrite {
+  let LIMITS: []int = [1, 2]
+  entry {
+    LIMITS[0] = 3
+    print(LIMITS[0])
+  }
+}

examples/rejected/module_var.ludic

@@ -0,0 +1,7 @@
+# 0.S: a module-level var is refused - a module's changing data is its state
+program ModuleVar {
+  var count: int = 0
+  entry {
+    print(count)
+  }
+}

examples/rejected/mut_not_state.ludic

@@ -0,0 +1,7 @@
+# 0.S: `mut` is for a state parameter
+program MutNotState {
+  function f(x: mut int) -> int { return x }
+  entry {
+    print(f(1))
+  }
+}

examples/rejected/state_mut_arg.ludic

@@ -0,0 +1,9 @@
+# 0.S: a read-only state is not handed on where a mut one is wanted
+program StateMutArg {
+  state Tally { n: int = 0 }
+  function bump(c: mut Tally) -> void { c.n += 1 }
+  function look(c: Tally) -> void { bump(c) }
+  entry (c: Tally) {
+    look(c)
+  }
+}

examples/rejected/state_readonly.ludic

@@ -0,0 +1,11 @@
+# 0.S: a state taken without `mut` is read-only - assigning through it is refused
+program StateReadonly {
+  state Tally { n: int = 0 }
+  function peek(c: Tally) -> int {
+    c.n = 1
+    return c.n
+  }
+  entry (c: Tally) {
+    print(peek(c))
+  }
+}