Introduce a new /delta command (#17903)

Release Notes:

- Added a new `/delta` command to re-insert changed files that were
previously included in a context.

---------

Co-authored-by: Roy <roy@anthropic.com>

crates/assistant/src/slash_command/default_command.rs

@@ -3,7 +3,7 @@ use crate::prompt_library::PromptStore;
 use anyhow::{anyhow, Result};
 use assistant_slash_command::{ArgumentCompletion, SlashCommandOutputSection};
 use gpui::{Task, WeakView};
-use language::LspAdapterDelegate;
+use language::{BufferSnapshot, LspAdapterDelegate};
 use std::{
     fmt::Write,
     sync::{atomic::AtomicBool, Arc},
@@ -43,6 +43,8 @@ impl SlashCommand for DefaultSlashCommand {
     fn run(
         self: Arc<Self>,
         _arguments: &[String],
+        _context_slash_command_output_sections: &[SlashCommandOutputSection<language::Anchor>],
+        _context_buffer: BufferSnapshot,
         _workspace: WeakView<Workspace>,
         _delegate: Option<Arc<dyn LspAdapterDelegate>>,
         cx: &mut WindowContext,
@@ -70,6 +72,7 @@ impl SlashCommand for DefaultSlashCommand {
                     range: 0..text.len(),
                     icon: IconName::Library,
                     label: "Default".into(),
+                    metadata: None,
                 }],
                 text,
                 run_commands_in_text: true,