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Remove accidental dead code (unused imports, the superseded paste tool()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 <noreply@anthropic.com>

src/modules/draw/clipboard/paste.rs

@@ -1,6 +1,6 @@
 // Paste tool — ribbon definition + CadCommand implementation.
 
-use crate::modules::{IconKind, ModuleEvent, ToolDef};
+use crate::modules::IconKind;
 
 /// Shared icon for the Paste button and its dropdown entries.
 pub const ICON: IconKind = IconKind::Svg(include_bytes!("../../../../assets/icons/paste.svg"));
@@ -13,15 +13,6 @@ pub const MENU_ITEMS: &[(&str, &str, IconKind)] = &[
     ("PASTEBLOCK", "Paste as Block", ICON),
 ];
 
-pub fn tool() -> ToolDef {
-    ToolDef {
-        id: "PASTECLIP",
-        label: "Paste",
-        icon: ICON,
-        event: ModuleEvent::Command("PASTECLIP".to_string()),
-    }
-}
-
 // ── CadCommand implementation ─────────────────────────────────────────────
 
 use acadrust::Handle;