feat: double-click component gates to edit their blueprint

Opens the component editor with the internal circuit loaded for
modification. On save, updates the component definition and all
existing instances in the main circuit.

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

js/state.js

@@ -41,5 +41,6 @@ export const state = {
     // Component Editor
     componentEditorActive: false,
     savedMainCircuit: null,  // { gates, connections, nextId } saved before entering editor
-    componentEditorName: ''
+    componentEditorName: '',
+    editingComponentId: null  // ID of component being edited (null = new component)
 };