fix: support local models by making thought field optional in Plan model (#601)

- Make thought field optional in Plan model to fix Pydantic validation errors with local models
- Add Ollama configuration example to conf.yaml.example
- Update documentation to include local model support
- Improve planner prompt with better JSON format requirements

Fixes local model integration issues where models like qwen3:14b would fail
due to missing thought field in JSON output.

Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

conf.yaml.example

@@ -13,6 +13,16 @@ BASIC_MODEL:
   # max_retries: 3 # Maximum number of retries for LLM calls
   # verify_ssl: false  # Uncomment this line to disable SSL certificate verification for self-signed certificates
 
+# Local model configuration example:
+
+# Ollama (Tested and supported for local development)
+# BASIC_MODEL:
+#   base_url: "http://localhost:11434/v1"  # Ollama OpenAI compatible endpoint
+#   model: "qwen3:14b"  # or "llama3.2", etc.
+#   api_key: "ollama"  # Ollama doesn't need real API key
+#   max_retries: 3
+#   verify_ssl: false  # Local deployment usually doesn't need SSL verification
+
 # To use Google Ai Studio as your basic platform:
 # BASIC_MODEL:
 #   platform: "google_aistudio"