feat(v2-alpha): add collapsible toolbox and refine binary simulator layout

- Introduce collapsible right-hand toolbox for the binary simulator
- Pin toolbox to the right edge with responsive fallback on smaller screens
- Rework tools and bit-width controls into a shared side layout
- Adjust control sizing, spacing, and visual hierarchy for clarity

Notes:
- Toolbox collapse is functional but requires refinement
- Tools and Bit Width should be merged into a single module/card
- Collapsed state does not yet fully hide the panel or re-centre content

Signed-off-by: Alexander Lyall <alex@adcm.uk>

src/scripts/binary.js

@@ -464,6 +464,17 @@
   /* -----------------------------
      EVENTS
   ----------------------------- */
+
+    // Collapsible right panel
+  const sidePanel = document.getElementById("sidePanel");
+  const btnPanelToggle = document.getElementById("btnPanelToggle");
+
+  btnPanelToggle?.addEventListener("click", () => {
+    sidePanel?.classList.toggle("isCollapsed");
+    // flip the chevron
+    btnPanelToggle.textContent = sidePanel?.classList.contains("isCollapsed") ? "❮" : "❯";
+  });
+
   modeToggle?.addEventListener("change", () => {
     updateUI();
   });
@@ -506,3 +517,4 @@
   updateModeHint();
   buildBits(bitCount);
 })();
+