Add LLM_PROVIDER to .env.example

Clarify where to set provider for vision tool routing.

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

.env.example

@@ -46,7 +46,10 @@ SPACE_ID=your_hf_space_id_here
 # Agent Configuration (Level 6 - Implementation Framework)
 # ============================================================================
 
-# LLM model selection: "gemini" or "claude"
+# LLM provider selection: "huggingface", "gemini", or "claude"
+LLM_PROVIDER=huggingface
+
+# LLM model selection: "gemini" or "claude" (used if LLM_PROVIDER not set)
 DEFAULT_LLM_MODEL=gemini
 
 # Search tool selection: "tavily" (free) or "exa" (paid)