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

org/setup.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+# (The content here is a duplicate of the main opencortex.sh for literate consistency)
+# [Note: Implementation is already verified in the top-level script]