Preserve sections generated by slash commands when reloading a context (#13199)

Release Notes:

- N/A

crates/assistant/src/slash_command/now_command.rs

@@ -53,9 +53,8 @@ impl SlashCommand for NowSlashCommand {
             text,
             sections: vec![SlashCommandOutputSection {
                 range,
-                render_placeholder: Arc::new(move |id, unfold, _cx| {
-                    NowPlaceholder { id, unfold, now }.into_any_element()
-                }),
+                icon: IconName::CountdownTimer,
+                label: now.to_rfc3339().into(),
             }],
             run_commands_in_text: false,
         }))