remove Hulls view tab and its supporting dead code

- VIEW_MODES: remove 'hulls' (gradient hull viz is now in the Hull node thumbnail)
- App.jsx: remove case 'hulls': from the refresh switch; remove 'hulls' entry
  from the accent color map
- lib.rs: remove the 'hulls' arm from get_pass_viz (per-pixel raster gradient
  render); update doc comment to reflect contours-only mode

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src-frontend/src/App.jsx

@@ -8,7 +8,7 @@ import { defaultPass, defaultGcodeConfig, PAPER_SIZES } from './store.js'
 import * as tauri from './hooks/useTauri.js'
 import { useFps } from './hooks/useFps.js'
 
-const VIEW_MODES = ['source', 'detection', 'hulls', 'contours', 'fill', 'gcode']
+const VIEW_MODES = ['source', 'detection', 'contours', 'fill', 'gcode']
 
 export default function App() {
   const [image, setImage]           = useState(null)
@@ -86,7 +86,6 @@ export default function App() {
         case 'detection':
           setDisplayB64(passes[activePass]?.vizB64 ?? null)
           break
-        case 'hulls':
         case 'contours':
           // Don't race getPassViz against generateFill — both need the AppState mutex.
           // filling=true means fill hasn't finished yet; the effect will re-run when it does.
@@ -372,7 +371,7 @@ export default function App() {
         {/* Top bar — accent colors match the section dots in the left panel */}
         <div className="flex items-center gap-1 px-3 py-2 border-b border-neutral-800 bg-neutral-900/80">
           {VIEW_MODES.map(m => {
-            const accent = { detection: '#6366f1', hulls: '#14b8a6', contours: '#14b8a6', fill: '#a855f7', gcode: '#f59e0b' }[m]
+            const accent = { detection: '#6366f1', contours: '#14b8a6', fill: '#a855f7', gcode: '#f59e0b' }[m]
             const label  = m === 'gcode' ? 'G-code' : m.charAt(0).toUpperCase() + m.slice(1)
             return (
               <button key={m}

src/lib.rs

@@ -706,8 +706,7 @@ fn compute_hull_holes(
     hull_holes
 }
 
-/// Return a viz image for an already-processed pass.
-/// mode: "hulls" | "contours"
+/// Return a contour SVG for an already-processed pass.
 #[tauri::command]
 fn get_pass_viz(pass_index: usize, mode: String, state: State<Mutex<AppState>>) -> Result<String, String> {
     let st  = state.lock().unwrap();
@@ -736,27 +735,6 @@ fn get_pass_viz(pass_index: usize, mode: String, state: State<Mutex<AppState>>)
     let hull_holes = compute_hull_holes(&pass.hulls, w, h);
 
     match mode.as_str() {
-        "hulls" => {
-            // Per-pixel raster: hull hue modulated by response intensity.
-            // intensity = (255 - response) / 255: max ink (resp=0) → full hue,
-            // threshold edge (resp≈threshold) → near black.
-            let response = &pass.response_map;
-            let mut rgba = vec![15u8; (w * h * 4) as usize];
-            for px in rgba.chunks_mut(4) { px[3] = 255; }
-
-            for hull in &pass.hulls {
-                let (hr, hg, hb) = hash_color(hull.id);
-                for &(px, py) in &hull.pixels {
-                    let resp = response.get((py * w + px) as usize).copied().unwrap_or(0);
-                    let intensity = (255u32 - resp as u32) as f32 / 255.0;
-                    let i = ((py * w + px) * 4) as usize;
-                    rgba[i]   = (hr as f32 * intensity) as u8;
-                    rgba[i+1] = (hg as f32 * intensity) as u8;
-                    rgba[i+2] = (hb as f32 * intensity) as u8;
-                }
-            }
-            Ok(rgba_to_b64_png(&rgba, w, h))
-        }
         "contours" => {
             let mut svg = format!(
                 r##"<svg xmlns="http://www.w3.org/2000/svg" width="{w}" height="{h}" viewBox="0 0 {w} {h}"><rect width="{w}" height="{h}" fill="#0f0f0f"/>"##