Refactor to use new ACP crate (#35043)

This will prepare us for running the protocol over MCP

Release Notes:

- N/A

---------

Co-authored-by: Ben Brandt <benjamin.j.brandt@gmail.com>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
Co-authored-by: Richard Feldman <oss@rtfeldman.com>

crates/agent_ui/src/agent_diff.rs

@@ -1506,8 +1506,7 @@ impl AgentDiff {
                     .read(cx)
                     .entries()
                     .last()
-                    .and_then(|entry| entry.diff())
-                    .is_some()
+                    .map_or(false, |entry| entry.diffs().next().is_some())
                 {
                     self.update_reviewing_editors(workspace, window, cx);
                 }
@@ -1517,8 +1516,7 @@ impl AgentDiff {
                     .read(cx)
                     .entries()
                     .get(*ix)
-                    .and_then(|entry| entry.diff())
-                    .is_some()
+                    .map_or(false, |entry| entry.diffs().next().is_some())
                 {
                     self.update_reviewing_editors(workspace, window, cx);
                 }