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

src/main/ipc-handlers.ts

@@ -0,0 +1,35 @@
+// src/main/ipc-handlers.ts
+import { ipcMain, BrowserWindow, nativeTheme, dialog } from 'electron'
+
+export function registerIpcHandlers(): void {
+  ipcMain.on('window:minimize', () => {
+    BrowserWindow.getFocusedWindow()?.minimize()
+  })
+
+  ipcMain.on('window:maximize', () => {
+    const win = BrowserWindow.getFocusedWindow()
+    if (win) win.isMaximized() ? win.unmaximize() : win.maximize()
+  })
+
+  ipcMain.on('window:close', () => {
+    BrowserWindow.getFocusedWindow()?.close()
+  })
+
+  ipcMain.handle('theme:get', () => nativeTheme.shouldUseDarkColors)
+
+  ipcMain.on('theme:set', (_event, theme: 'system' | 'dark' | 'light') => {
+    nativeTheme.themeSource = theme
+  })
+
+  ipcMain.handle('dialog:openFile', async (_event, options: Electron.OpenDialogOptions) => {
+    const win = BrowserWindow.getFocusedWindow()
+    if (!win) return null
+    const result = await dialog.showOpenDialog(win, options)
+    if (result.canceled || result.filePaths.length === 0) return null
+    const fs = await import('fs')
+    try {
+      const content = fs.readFileSync(result.filePaths[0], 'utf-8')
+      return { path: result.filePaths[0], content }
+    } catch { return null }
+  })
+}