feat: expose Helix in the Draw expansion

assets/icons/helix.svg

@@ -0,0 +1,3 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" role="img" aria-label="Helix" fill="none" stroke-linecap="round" stroke-linejoin="round">
+  <path d="M5 4C5 0 20 2 19 6C18 10 4 7 4 12C4 17 20 12 20 17C20 22 5 24 5 19C5 15 19 18 19 12C19 8 5 12 5 7" stroke="#B4B6B9" stroke-width="1.6"/><circle cx="5" cy="4" r="1.3" fill="#6DB7ED" stroke="none"/>
+</svg>

src/ui/ribbon/draw_tools/11_helix.rs

@@ -0,0 +1,6 @@
+Tool {
+    command: "HELIX",
+    label: "Helix",
+    icon: include_bytes!(concat!(env!("CARGO_MANIFEST_DIR"), "/assets/icons/helix.svg")),
+    options: &[],
+}