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 <[email protected]>

src/scene/pipeline/wire_gpu.rs

@@ -123,13 +123,6 @@ impl WireGpu {
         g
     }
 
-    /// Creates a ghost copy with `alpha` applied on top of the wire's own alpha.
-    #[allow(dead_code)]
-    pub fn new_ghost(device: &wgpu::Device, wire: &WireModel, alpha: f32) -> Self {
-        let [r, g, b, a] = wire.color;
-        Self::build(device, wire, [r, g, b, a * alpha])
-    }
-
     /// Merge multiple WireModels into GPU buffers chunked to fit the 256 MB GPU limit.
     /// Each wire keeps its own color and pattern — they're stored per-vertex.
     /// Returns an empty Vec if the combined vertex list is empty.