Add user-visible output for remote operations (#25849)

This PR adds toasts for reporting success and errors from remote git
operations. This PR also adds a focus handle to notifications, in
anticipation of making them keyboard accessible.

Release Notes:

- N/A

---------

Co-authored-by: julia <julia@zed.dev>

crates/editor/src/signature_help.rs

@@ -310,7 +310,7 @@ impl SignatureHelpPopover {
             .child(
                 div().px_4().pb_1().child(
                     StyledText::new(self.label.clone())
-                        .with_highlights(&self.style, self.highlights.iter().cloned()),
+                        .with_default_highlights(&self.style, self.highlights.iter().cloned()),
                 ),
             )
             .into_any_element()