Fix failing unit tests

* This PR caused the Sidebar.test.ts file tests to fail because TransformStream is not found.
* TransformStream exists in the Node version I'm testing with (20), but it still isn't found by Jest
* Turns out it is a problem with Jest, and the workaround is the simple package jest-fixed-jsdom, which subclasses JSDOMEnvironment testing environment, placing this and several other dependencies in its global object.

* In package.json
  - add jest-fixed-jsdom as a devDependency

* In jest.config.cjs
  - change testEnvironment to jest-fixed-jsdom

client/jest.config.cjs

@@ -1,6 +1,6 @@
 module.exports = {
   preset: "ts-jest",
-  testEnvironment: "jsdom",
+  testEnvironment: "jest-fixed-jsdom",
   moduleNameMapper: {
     "^@/(.*)$": "<rootDir>/src/$1",
     "\\.css$": "<rootDir>/src/__mocks__/styleMock.js",

package-lock.json

@@ -31,6 +31,7 @@
         "@types/jest": "^29.5.14",
         "@types/node": "^22.7.5",
         "@types/shell-quote": "^1.7.5",
+        "jest-fixed-jsdom": "^0.0.9",
         "prettier": "3.3.3",
         "typescript": "^5.4.2"
       }
@@ -5358,6 +5359,19 @@
         "node": "^14.15.0 || ^16.10.0 || >=18.0.0"
       }
     },
+    "node_modules/jest-fixed-jsdom": {
+      "version": "0.0.9",
+      "resolved": "https://registry.npmjs.org/jest-fixed-jsdom/-/jest-fixed-jsdom-0.0.9.tgz",
+      "integrity": "sha512-KPfqh2+sn5q2B+7LZktwDcwhCpOpUSue8a1I+BcixWLOQoEVyAjAGfH+IYZGoxZsziNojoHGRTC8xRbB1wDD4g==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=18.0.0"
+      },
+      "peerDependencies": {
+        "jest-environment-jsdom": ">=28.0.0"
+      }
+    },
     "node_modules/jest-get-type": {
       "version": "29.6.3",
       "dev": true,

package.json

@@ -52,6 +52,7 @@
     "@types/jest": "^29.5.14",
     "@types/node": "^22.7.5",
     "@types/shell-quote": "^1.7.5",
+    "jest-fixed-jsdom": "^0.0.9",
     "prettier": "3.3.3",
     "typescript": "^5.4.2"
   }