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/snap_popup.rs

@@ -233,27 +233,3 @@ const LABEL_OFF: Color = Color {
     a: 1.0,
 };
 
-/// The `Point` parameter is unused today; kept for future tooltip positioning.
-#[allow(dead_code)]
-pub fn snap_marker_color(snap_type: SnapType) -> Color {
-    match snap_type {
-        SnapType::Endpoint | SnapType::Midpoint => Color {
-            r: 1.0,
-            g: 0.9,
-            b: 0.1,
-            a: 1.0,
-        },
-        SnapType::Grid => Color {
-            r: 0.4,
-            g: 0.9,
-            b: 0.4,
-            a: 1.0,
-        },
-        _ => Color {
-            r: 1.0,
-            g: 0.9,
-            b: 0.1,
-            a: 1.0,
-        },
-    }
-}