fix(ci): run playwright from e2e/, npx --prefix does not change the cwd

`npx --prefix e2e playwright test` resolves the binary but keeps the working
directory, so playwright would look for playwright.config.js in the app root,
find none, and run with defaults against no tests. Caught before tonight's first
scheduled run.

.forgejo/workflows/e2e.yml

@@ -110,9 +110,13 @@ jobs:
           set -e
           cd src
           mongosh --host mongo --quiet fuegos e2e/seed.js
-          npm --prefix e2e ci --no-audit --no-fund
-          npx --prefix e2e playwright install --with-deps chromium
-          npx --prefix e2e playwright test
+          # Dentro de e2e/: playwright busca su playwright.config.js en el
+          # directorio de trabajo, y `npx --prefix` resuelve el binario pero NO
+          # cambia el cwd (correría sin config y sin encontrar los tests).
+          cd e2e
+          npm ci --no-audit --no-fund
+          npx playwright install --with-deps chromium
+          npx playwright test
 
       # Sin `actions/upload-artifact` (action JS, ver fase 9 §3): al menos el log
       # del servidor y la lista de trazas quedan en la salida del job.