Ensure rejecting a hunk dismisses the diff (#27919)

Release Notes:

- N/A

crates/assistant_tools/src/edit_files_tool.rs

@@ -339,6 +339,8 @@ impl EditToolRequest {
             }
             DiffResult::Diff(diff) => {
                 cx.update(|cx| {
+                    self.action_log
+                        .update(cx, |log, cx| log.buffer_read(buffer.clone(), cx));
                     buffer.update(cx, |buffer, cx| {
                         buffer.finalize_last_transaction();
                         buffer.apply_diff(diff, cx);

crates/assistant_tools/src/find_replace_file_tool.rs

@@ -226,6 +226,9 @@ impl Tool for FindReplaceFileTool {
             };
 
             let snapshot = cx.update(|cx| {
+                action_log.update(cx, |log, cx| {
+                    log.buffer_read(buffer.clone(), cx)
+                });
                 let snapshot = buffer.update(cx, |buffer, cx| {
                     buffer.finalize_last_transaction();
                     buffer.apply_diff(diff, cx);