feat: add DeepSeek and NVIDIA NIM providers

- Add deepseek and nvidia entries to gateway-provider config

- Add DEEPSEEK_API_KEY and NVIDIA_API_KEY to .env.example

- Add deepseek and nvidia to doctor's LLM provider check

- Fix remaining harness-log → log-message reference

.github/workflows/lint.yml

@@ -82,6 +82,6 @@ jobs:
 
       - name: Check README has quick install
         run: |
-          grep -q "curl.*opencortex" README.org && \
+          grep -q "curl.*passepartout" README.org && \
             echo "OK: Quick install in README" || \
             echo "WARNING: Quick install curl command not found in README"