Add the ability to follow the agent as it makes edits (#29839)

Nathan here: I also tacked on a bunch of UI refinement.

Release Notes:

- Introduced the ability to follow the agent around as it reads and
edits files.

---------

Co-authored-by: Nathan Sobo <nathan@zed.dev>
Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

crates/assistant_tools/src/streaming_edit_file_tool.rs

@@ -170,7 +170,7 @@ impl Tool for StreamingEditFileTool {
                 .update(|cx| LanguageModelRegistry::read_global(cx).default_model())?
                 .context("default model not set")?
                 .model;
-            let edit_agent = EditAgent::new(model, action_log, Templates::new());
+            let edit_agent = EditAgent::new(model, project.clone(), action_log, Templates::new());
 
             let buffer = project
                 .update(cx, |project, cx| {