Implement Immortal DOM to prevent null pointer crashes in challenge script

src/duckai.ts

@@ -39,6 +39,24 @@ export class DuckAI {
         configurable: true
       });
 
+      // IMMORTAL DOM Strategy: Never return null
+      const originalGetElementById = window.document.getElementById;
+      window.document.getElementById = function(id: string) {
+          const el = originalGetElementById.call(this, id);
+          if (el) return el;
+          // Return a dummy div if not found to prevent crash
+          return window.document.createElement('div');
+      };
+
+      const originalQuerySelector = window.document.querySelector;
+      window.document.querySelector = function(selector: string) {
+          try {
+              const el = originalQuerySelector.call(this, selector);
+              if (el) return el;
+          } catch(e) {}
+          return window.document.createElement('div');
+      };
+
       // Also keep the createElement hook just in case
       const originalCreateElement = window.document.createElement;
       window.document.createElement = function(tagName: string) {