chore: remove dead UI helpers and orphan toolbar stubs

Each item below was gated by #[allow(dead_code)] and has zero callers
across src/ — none of them are part of any public API consumed by
external crates (this is a binary, not a library):

* modules/insert/underlay_frames.rs + edit_aliases.rs — toolbar stubs
  whose `tool()` registrars were never wired into the ribbon; the
  parent mod.rs inlines its own include_bytes! for the SVGs, so the
  files were orphan dead weight.
* ui/snap_popup.rs:snap_marker_color — never called.
* ui/ribbon/mod.rs:last_dropdown_cmd — never called.
* ui/scale_popup.rs:anno_scale_for_label — never called.
* ui/layers.rs:color_name_to_aci — inverse of aci_color_display
  with zero call sites.
* linetypes.rs:name_list — never called.
* scene/pipeline/wire_gpu.rs:new_ghost — never called.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/ui/layers.rs

@@ -838,22 +838,6 @@ fn color_label_aci(i: u8) -> &'static str {
     }
 }
 
-#[allow(dead_code)]
-fn color_name_to_aci(name: &str) -> u8 {
-    match name {
-        "red" => 1,
-        "yellow" => 2,
-        "green" => 3,
-        "cyan" => 4,
-        "blue" => 5,
-        "magenta" => 6,
-        "white" => 7,
-        "dark gray" => 8,
-        "gray" => 9,
-        _ => 7,
-    }
-}
-
 pub fn iced_color_from_acad(c: &AcadColor) -> Color {
     match c {
         AcadColor::Index(i) => {