Allow editing Agent2 messages (#36155)

Release Notes:

- N/A

---------

Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Agus Zubiaga <agus@zed.dev>

crates/agent2/src/thread.rs

@@ -124,12 +124,12 @@ impl UserMessage {
                 }
                 UserMessageContent::Mention { uri, content } => {
                     match uri {
-                        MentionUri::File(path) => {
+                        MentionUri::File { abs_path, .. } => {
                             write!(
                                 &mut symbol_context,
                                 "\n{}",
                                 MarkdownCodeBlock {
-                                    tag: &codeblock_tag(&path, None),
+                                    tag: &codeblock_tag(&abs_path, None),
                                     text: &content.to_string(),
                                 }
                             )