phase: 20.49 COMPLETE; 20.50 Flow+String minimal reps; 20.51 selfhost v0/v1 minimal (Option A/B); hv1-inline binop/unop/copy; docs + run_all + CURRENT_TASK -> 21.0

examples/jit_map_policy_demo.hako

@@ -0,0 +1,19 @@
+// @jit-debug
+// @plugin-builtins
+
+// MapBox end-to-end via InvokePolicy/Observe
+// - Exercises: size/get/has/set on plugin-builtins path
+
+static box Main {
+  main() {
+    local m, ok, v, sz
+    m = new MapBox()
+    m.set(1, 100)
+    m.set(2, 200)
+    ok = m.has(1)
+    v = m.get(1)
+    sz = m.size()
+    return sz  // expect: 2
+  }
+}
+