feat(phase1): architecture skeleton

- Electron 33 main process with frameless window, IPC, win-state persistence
- Preload with contextBridge typed API (window, theme, dialog)
- Vue 3 + Pinia + Element Plus + Vue Router renderer
- Dark/light dual theme via CSS custom properties
- TitleBar with window controls + theme toggle
- StatusBar placeholder
- Design spec document

.gitignore

@@ -16,3 +16,6 @@ yarn-error.log*
 
 # Legacy codebase — archived Vue 2 version, not part of v2 build
 legacy/
+
+# Brainstorming artifacts
+.superpowers/