Fix asyncImportHelper to use relative paths for rollup preprocessing

Changed asyncImportHelper.ts to use relative path (../../dist/jspdf.es.js) instead of
absolute Karma path (/base/dist/jspdf.es.js). Configured rollup external option to
preserve relative import paths. This matches the ESM deployment test approach.

Author: claude

test/deployment/esm/karma.conf.js

@@ -63,6 +63,7 @@ module.exports = config => {
         resolve(),
         commonjs()
       ],
+      external: [/^\.\.?\//],  // Mark relative paths as external
       output: {
         format: "esm",
         sourcemap: "inline"

test/unit/asyncImportHelper.ts

@@ -12,7 +12,7 @@ import {
   AcroFormTextField,
   AcroFormPasswordField,
   AcroFormAppearance
-} from "/base/dist/jspdf.es.js";
+} from "../../dist/jspdf.es.js";
 
 window.importsReady({
   jsPDF,

test/unit/karma.conf.js

@@ -49,6 +49,7 @@ module.exports = config => {
         resolve(),
         commonjs()
       ],
+      external: [/^\.\.?\//],  // Mark relative paths as external
       output: {
         format: "esm",
         sourcemap: "inline"