Add cloud credentials to CI workflow so cloud tests run

The CI workflow runs all tests but was not setting NDI_CLOUD_USERNAME
and NDI_CLOUD_PASSWORD, causing every cloud test to be skipped. Map
the TEST_USER_2 secrets so cloud integration tests actually execute.

https://claude.ai/code/session_01A7rAxYf5pSvs19iVJe3ncL

Author: claude

.github/workflows/ci.yml

@@ -52,6 +52,9 @@ jobs:
         run: python -m ndi check
 
       - name: Run tests with coverage
+        env:
+          NDI_CLOUD_USERNAME: ${{ secrets.TEST_USER_2_USERNAME }}
+          NDI_CLOUD_PASSWORD: ${{ secrets.TEST_USER_2_PASSWORD }}
         run: |
           # Use sys.monitoring (PEP 669) on Python 3.12+ for faster coverage.
           # CTracer (sys.settrace) is catastrophically slow on 3.12 when