fix(pdfjs-annotation-viewer): initialize konvaClientRect dimensions and add HASH_PARAMS implementation

Updated the pdfjs-annotation-extension-testdata.json to set default dimensions for konvaClientRect to zero. Added a HASH_PARAMS implementation in viewer.html to handle hash parsing, ensuring compatibility with the pdfjs-annotation-extension bundle and preventing runtime errors.

public/pdfjs-annotation-viewer/web/viewer.html

@@ -34,6 +34,27 @@ See https://github.com/adobe-type-tools/cmap-resources
     <link rel="stylesheet" href="viewer.css">
 
   <script src="viewer.mjs" type="module"></script>
+  <script>
+    // Provide a minimal HASH_PARAMS implementation expected by the
+    // pdfjs-annotation-extension bundle. It mirrors the core viewer's
+    // hash parsing behaviour enough to avoid runtime errors.
+    (function () {
+      if (window.HASH_PARAMS) {
+        return;
+      }
+      const hash = window.location.hash || "";
+      const raw = hash.startsWith("#") ? hash.slice(1) : hash;
+      const params = new URLSearchParams(raw);
+      window.HASH_PARAMS = {
+        get(name) {
+          // Always return a string to avoid null/undefined consumers
+          // calling .slice()/etc. on a non-string value.
+          const v = params.get(name);
+          return v == null ? "" : String(v);
+        },
+      };
+    })();
+  </script>
   <script src="./pdfjs-annotation-extension/pdfjs-annotation-extension.js" type="module"></script>
   </head>