agent: Render diffs for the edit file tool (#29234)

This PR implements the `ToolCard` for the edit file tool, which allow us
to display an editor with a diff in the thread view with the changes
performed by the model.

- [x] Fix buffer sometimes displaying empty
- [x] Stop buffer from scrolling together with the thread
- [x] Fix multibuffer header sometimes appearing
- [x] Fix buffer height issue
- [x] Implement "full height" expand button
- [x] Add "Jump To File" functionality
- [x] Polish and refine styles

Release Notes:

- agent: Added diff preview cards in the thread view for edits performed
by the agent.

---------

Co-authored-by: João Marcos <marcospb19@hotmail.com>
Co-authored-by: Richard Feldman <oss@rtfeldman.com>
Co-authored-by: Agus Zubiaga <hi@aguz.me>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/assistant_tools/Cargo.toml

@@ -14,9 +14,11 @@ path = "src/assistant_tools.rs"
 [dependencies]
 anyhow.workspace = true
 assistant_tool.workspace = true
+buffer_diff.workspace = true
 chrono.workspace = true
 collections.workspace = true
 component.workspace = true
+editor.workspace = true
 futures.workspace = true
 gpui.workspace = true
 html_to_markdown.workspace = true
@@ -35,6 +37,7 @@ serde_json.workspace = true
 ui.workspace = true
 util.workspace = true
 web_search.workspace = true
+workspace.workspace = true
 workspace-hack.workspace = true
 worktree.workspace = true
 zed_llm_client.workspace = true