Update .env.example: NN model as default provider

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.env.example

@@ -1,7 +1,12 @@
-# LLM Provider: anthropic, ollama, groq
-LLM_PROVIDER=ollama
-OLLAMA_MODEL=llama3.1
+# LLM Provider: nn (default), anthropic, ollama, groq, gemini
+# NN is the default — free, fast, no API key needed.
+# Leave LLM_PROVIDER unset or set to "nn" to use the local ONNX model.
+#LLM_PROVIDER=nn
+
+# Uncomment for Ollama:
+#LLM_PROVIDER=ollama
+#OLLAMA_MODEL=llama3.1
 
 # Uncomment for Groq:
-# LLM_PROVIDER=groq
-# GROQ_API_KEY=your_groq_api_key_here
+#LLM_PROVIDER=groq
+#GROQ_API_KEY=your_groq_api_key_here