docs: Updated the docs to include details on the new agent spawning system and built-in user interaction tools

docs/REPL.md

@@ -50,6 +50,9 @@ things like
 * **Configurable Keybindings:** You can switch between `emacs` style keybindings or `vi` style keybindings
 * [**Custom REPL Prompt:**](./REPL-PROMPT.md) You can even customize the REPL prompt to display information about the 
   current context in the prompt
+* **Built-in user interaction tools:** When function calling is enabled in the REPL, the `user__ask`, `user__confirm`,
+  `user__input`, and `user__checkbox` tools are always available for interactive prompts. These are not injected in the
+  one-shot CLI mode.
 
 ---
 
@@ -247,4 +250,4 @@ The `.exit` command is used to move between modes in the Loki REPL.
 
 ### `.help` - Show the help guide
 Just like with any shell or REPL, you sometimes need a little help and want to know what commands are available to you.
-That's when you use the `.help` command.
+That's when you use the `.help` command.