Point clouds: attach dialog, crop toolbar, stylize, palette rows

POINTCLOUDATTACH opens the Attach Point Cloud dialog after the file is
chosen; its Attach button lives in the Attach Underlay list instead of a
separate Insert panel. A selected cloud brings the crop tools to the
right-edge toolbar. POINTCLOUDSTYLIZE sets the stylization with the
reference's prompts, the External References palette lists point clouds
(unload, reload, detach, path), and definitions keep the header extents.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/modules/draw/select.rs

@@ -124,6 +124,13 @@ impl SelectObjectsCommand {
         command
     }
 
+    /// The standard gather with the command's own wording.
+    pub fn with_prompt(prompt_cmd: &str, pending_cmd: &str, prompt_text: &'static str) -> Self {
+        let mut command = Self::plain(prompt_cmd, pending_cmd);
+        command.prompt_text = Some(prompt_text);
+        command
+    }
+
     pub fn auto_constrain(pending_cmd: &str) -> Self {
         let mut command = Self::new(pending_cmd);
         command.auto_constrain_settings = true;