chore: move dormant prototypes to reference/ directory

- game/npc-logic.js → reference/npc-logic.js (added REFERENCE PROTOTYPE header)
- scripts/guardrails.js → reference/guardrails.js (added REFERENCE PROTOTYPE header)
- New reference/README.md with integration instructions

Closes #196

reference/README.md

@@ -0,0 +1,18 @@
+# reference/
+
+Dormant prototypes not loaded by the browser runtime.
+
+## Files
+
+| File | Why dormant |
+|------|-------------|
+| `npc-logic.js` | Uses ES module syntax (`export default`) — incompatible with `<script>` tag loading |
+| `guardrails.js` | Has inline test code at the bottom — not production-ready |
+
+## To integrate
+
+1. Refactor to remove ES module exports (`npc-logic.js`)
+2. Remove inline test code (`guardrails.js`)
+3. Add `<script src="reference/filename.js">` to `index.html`
+4. Wire into game engine lifecycle
+5. Add tests

reference/guardrails.js

@@ -1,3 +1,12 @@
+/**
+ * REFERENCE PROTOTYPE — NOT LOADED BY RUNTIME
+ *
+ * This file is dormant. It contains inline test code at the bottom
+ * and is not production-ready.
+ *
+ * To integrate: remove the inline test block, add <script src="reference/guardrails.js">
+ * to index.html, and wire Guardrails into the game engine lifecycle.
+ */
 
 /**
  * Symbolic Guardrails for The Beacon

reference/npc-logic.js

@@ -1,3 +1,12 @@
+/**
+ * REFERENCE PROTOTYPE — NOT LOADED BY RUNTIME
+ *
+ * This file is dormant. It uses ES module syntax (export default),
+ * which is incompatible with <script> tag loading.
+ *
+ * To integrate: remove the default export, add <script src="reference/npc-logic.js">
+ * to index.html, and wire NPCStateMachine into the game engine lifecycle.
+ */
 
 class NPCStateMachine {
     constructor(states) {