test(e2e): add jiti devDep, derive repo root from import.meta.url

'npm run test:e2e' was failing before it even started:
the four tests import { createJiti } from 'jiti' but jiti was never
declared in package.json, so Node threw ERR_MODULE_NOT_FOUND on the
first import. Adding it to devDependencies fixes the loader.

The same tests hard-coded the original developer's path
('/home/moze/Sorgenti/pi-imgen'), so even with jiti installed they
would have failed on any other checkout. Replacing it with
dirname(dirname(dirname(fileURLToPath(import.meta.url)))) lets the
suite run from wherever the repo is cloned.

package-lock.json

@@ -13,6 +13,7 @@
       },
       "devDependencies": {
         "@types/node": "^20.14.0",
+        "jiti": "^2.4.0",
         "typescript": "^5.6.0"
       },
       "engines": {
@@ -3515,6 +3516,16 @@
         "node": ">= 4"
       }
     },
+    "node_modules/jiti": {
+      "version": "2.7.0",
+      "resolved": "https://registry.npmjs.org/jiti/-/jiti-2.7.0.tgz",
+      "integrity": "sha512-AC/7JofJvZGrrneWNaEnJeOLUx+JlGt7tNa0wZiRPT4MY1wmfKjt2+6O2p2uz2+skll8OZZmJMNqeke7kKbNgQ==",
+      "dev": true,
+      "license": "MIT",
+      "bin": {
+        "jiti": "lib/jiti-cli.mjs"
+      }
+    },
     "node_modules/json-bigint": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/json-bigint/-/json-bigint-1.0.0.tgz",