chore: clear compiler warnings

Remove accidental dead code (unused imports, the superseded paste tool()
helper, a never-read TORIENT handles field, a duplicate let binding, an
unneeded mut) and mark intentional-but-unwired scaffolding with
allow(dead_code): the web-only save_to_bytes, the plugin loadable() probe,
the planned PICK_HIGHLIGHT colours, the DynFieldSpec label, and the layout
ribbon helpers. Native build is now warning-clean apart from the upstream
nom/quick-xml future-incompat notices.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/app/commands.rs

@@ -1204,7 +1204,7 @@ impl OpenCADStudio {
                     let cam_rot = self.tabs[i].scene.camera.borrow().rotation;
                     let right = cam_rot * glam::Vec3::X;
                     let view_twist = right.y.atan2(right.x) as f64;
-                    let new_cmd = TorientCommand::new(handles, entities, view_twist);
+                    let new_cmd = TorientCommand::new(entities, view_twist);
                     self.command_line.push_info(&new_cmd.prompt());
                     self.tabs[i].active_cmd = Some(Box::new(new_cmd));
                 }

src/app/style_ops.rs

@@ -47,7 +47,7 @@ impl OpenCADStudio {
     /// sorted by name so the `HashMap` backing them renders stably).
     pub(super) fn style_names(&self, kind: StyleKind) -> Vec<String> {
         let doc = &self.tabs[self.active_tab].scene.document;
-        let mut from_objects = |pick: fn(&ObjectType) -> Option<&str>| -> Vec<String> {
+        let from_objects = |pick: fn(&ObjectType) -> Option<&str>| -> Vec<String> {
             let mut v: Vec<String> = doc
                 .objects
                 .values()

src/app/update.rs

@@ -1677,7 +1677,6 @@ impl OpenCADStudio {
                 // buffer to the same submit path so typing a command name (or
                 // an option keyword like "R") and pressing Enter works without
                 // first clicking into the command line (issue #99).
-                let i = self.active_tab;
                 if !self.command_line.input.trim().is_empty() {
                     return self.update(Message::CommandSubmit);
                 }