Add support for on-demand involvement

Fixes https://github.com/etkecc/baibot/issues/15

src/conversation/mod.rs

@@ -2,4 +2,6 @@ pub(crate) mod llm;
 pub(crate) mod matrix;
 mod matrix_llm_bridge;
 
-pub(crate) use matrix_llm_bridge::create_llm_conversation_for_matrix_thread;
+pub(crate) use matrix_llm_bridge::{
+    create_llm_conversation_for_matrix_reply_chain, create_llm_conversation_for_matrix_thread,
+};