feat: sectioned toolbar + custom component editor

- Redesigned toolbar with I/O, Gates, and Components sections
- Component editor: sub-canvas mode to design reusable chips
  - Save/Cancel with main circuit state preservation
  - Components persist in localStorage
- Custom components render as purple chips with dynamic I/O ports
- Component evaluation simulates internal circuit as black box
- Toolbar height increased to 56px for section labels
- All height references updated consistently

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

js/state.js

@@ -36,5 +36,10 @@ export const state = {
     simSpeed: 500,       // ms per tick
 
     // Puzzle/Components
-    customComponents: {}  // { id -> component definition }
+    customComponents: {},  // { id -> component definition }
+
+    // Component Editor
+    componentEditorActive: false,
+    savedMainCircuit: null,  // { gates, connections, nextId } saved before entering editor
+    componentEditorName: ''
 };