Introduce a new /tabs command (#12382)

This inserts the content of the open tabs sorted by recency.

Release Notes:

- N/A

---------

Co-authored-by: Nathan <nathan@zed.dev>

crates/assistant/src/slash_command.rs

@@ -21,6 +21,7 @@ pub mod file_command;
 pub mod project_command;
 pub mod prompt_command;
 pub mod search_command;
+pub mod tabs_command;
 
 pub(crate) struct SlashCommandCompletionProvider {
     editor: WeakView<ConversationEditor>,