fix(build): add esbuild fallback plugin for standalone CI builds

When axe-core builds outside the a11y-engine monorepo, the relative
import to ip-protection/utils/fingerprint fails. Added an esbuild
resolve plugin that falls back to a stub returning null when the real
file is unavailable. In the monorepo, the real fingerprint is used.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Abhishek Bindra

build/tasks/esbuild.js

@@ -1,5 +1,29 @@
 const { build } = require('esbuild');
 const path = require('path');
+const fs = require('fs');
+
+// [a11y-core]: resolve ip-protection imports to real file in monorepo,
+// or fall back to a stub when building axe-core standalone (CI).
+const fingerprintFallback = {
+  name: 'a11y-fingerprint-fallback',
+  setup(pluginBuild) {
+    pluginBuild.onResolve(
+      { filter: /ip-protection\/utils\/fingerprint/ },
+      args => {
+        const realPath = path.resolve(args.resolveDir, args.path + '.js');
+        if (fs.existsSync(realPath)) {
+          return { path: realPath };
+        }
+        return {
+          path: path.resolve(
+            __dirname,
+            '../../lib/core/utils/fingerprint-stub.js'
+          )
+        };
+      }
+    );
+  }
+};
 
 module.exports = function (grunt) {
   grunt.registerMultiTask(
@@ -24,7 +48,8 @@ module.exports = function (grunt) {
             outfile: path.join(dest, name),
             minify: false,
             format: 'esm',
-            bundle: true
+            bundle: true,
+            plugins: [fingerprintFallback]
           })
             .then(done)
             .catch(e => {

lib/core/utils/fingerprint-stub.js

@@ -0,0 +1,7 @@
+// Fallback stub used when axe-core builds outside the a11y-engine monorepo.
+// The real fingerprint logic lives in ip-protection/utils/fingerprint.js
+// and is resolved by the esbuild plugin during monorepo builds.
+// eslint-disable-next-line no-unused-vars
+export function computeFingerprintHash(_outerHTML) {
+  return null;
+}