Implement SQLite support check for Chroma's trigram tokenizer, enhancing compatibility with cloud environments. Update README for model command syntax and add pysqlite3-binary to requirements for improved SQLite functionality.

README.md

@@ -73,8 +73,8 @@ python main.py
 - `/models current`
 - `/models add <model_name>`
 - `/models add <key> <provider> <model_name> [api_base]`
-- `/models switch <key>`
-- `/models remove <key>`
+- `/models switch <key|index>`
+- `/models remove <key|index>`
 
 说明：
 - `/models add <model_name>` 只替换模型名，沿用当前 API Base 和 API Key