feat: bootstrap secure cross-platform assistant

Establish the Electron foundation and pluggable agent runtime so desktop workflows can evolve safely across supported platforms.

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

src/main/window.ts

@@ -0,0 +1,80 @@
+import { BrowserWindow, shell } from 'electron'
+import { dirname, join } from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+const currentDirectory = dirname(fileURLToPath(import.meta.url))
+
+function isAllowedExternalUrl(url: string): boolean {
+  try {
+    return new URL(url).protocol === 'https:'
+  } catch {
+    return false
+  }
+}
+
+export function createMainWindow(shouldQuit: () => boolean): BrowserWindow {
+  const window = new BrowserWindow({
+    width: 1180,
+    height: 760,
+    minWidth: 920,
+    minHeight: 620,
+    show: false,
+    backgroundColor: '#f4f1ea',
+    titleBarStyle: process.platform === 'darwin' ? 'hiddenInset' : 'default',
+    webPreferences: {
+      preload: join(currentDirectory, '../preload/index.cjs'),
+      contextIsolation: true,
+      nodeIntegration: false,
+      sandbox: true
+    }
+  })
+
+  window.once('ready-to-show', () => {
+    window.show()
+  })
+
+  window.on('close', (event) => {
+    if (!shouldQuit()) {
+      event.preventDefault()
+      window.hide()
+    }
+  })
+
+  window.webContents.setWindowOpenHandler(({ url }) => {
+    if (isAllowedExternalUrl(url)) {
+      void shell.openExternal(url)
+    }
+    return { action: 'deny' }
+  })
+
+  window.webContents.on('will-navigate', (event, url) => {
+    const developmentUrl = process.env.ELECTRON_RENDERER_URL
+    if (!developmentUrl || !url.startsWith(developmentUrl)) {
+      event.preventDefault()
+    }
+  })
+
+  if (process.env.ELECTRON_RENDERER_URL) {
+    void window.loadURL(process.env.ELECTRON_RENDERER_URL)
+  } else {
+    void window.loadFile(join(currentDirectory, '../renderer/index.html'))
+  }
+
+  return window
+}
+
+export function showWindow(window: BrowserWindow): void {
+  if (window.isMinimized()) {
+    window.restore()
+  }
+  window.show()
+  window.focus()
+}
+
+export function toggleWindow(window: BrowserWindow): void {
+  if (window.isVisible() && window.isFocused()) {
+    window.hide()
+    return
+  }
+  showWindow(window)
+}