feat(desktop): show native error dialogs on startup failures

Replace silent console.error + app.quit() with dialog.showErrorBox()
so users actually see why the app failed to start instead of it just
disappearing. Covers server spawn errors, timeout, port allocation
failure, mid-session server crashes, and window creation failures.

apps/desktop/src/main/index.ts

@@ -1,7 +1,7 @@
 import { spawn } from 'node:child_process'
 import { createServer } from 'node:net'
 import { join } from 'node:path'
-import { app, BrowserWindow, shell } from 'electron'
+import { app, BrowserWindow, dialog, shell } from 'electron'
 import killProcessTree from 'tree-kill'
 
 const DEV_SERVER_URL = 'http://localhost:3000'
@@ -9,10 +9,17 @@ const DEV_SERVER_URL = 'http://localhost:3000'
 let mainWindow: BrowserWindow | null = null
 let serverProcess: ReturnType<typeof spawn> | null = null
 let isQuitting = false
+let serverReady = false
 
 const shouldAbortWindowLoad = (): boolean =>
   isQuitting || !mainWindow || mainWindow.isDestroyed()
 
+const showErrorAndQuit = (title: string, detail: string) => {
+  if (isQuitting) return
+  dialog.showErrorBox(title, detail)
+  app.quit()
+}
+
 const getAvailablePort = (): Promise<number> =>
   new Promise((resolve, reject) => {
     const server = createServer()
@@ -84,10 +91,22 @@ const spawnServer = (port: number): string => {
 
   serverProcess.on('error', (err) => {
     console.error('Failed to start server:', err)
+    showErrorAndQuit(
+      'Startup Failed',
+      'A required component failed to start. Please reinstall the app.',
+    )
   })
 
-  serverProcess.on('exit', () => {
+  serverProcess.on('exit', (code) => {
     serverProcess = null
+    if (!isQuitting && serverReady) {
+      showErrorAndQuit(
+        'Service Stopped',
+        app.isPackaged
+          ? 'The background service stopped unexpectedly. Please restart the app.'
+          : `Server process exited unexpectedly (code ${code}). Check the server logs for details.`,
+      )
+    }
   })
 
   return `http://127.0.0.1:${port}`
@@ -98,7 +117,16 @@ const resolveServerUrl = async (): Promise<string | null> => {
     return DEV_SERVER_URL
   }
 
-  const port = await getAvailablePort()
+  let port: number
+  try {
+    port = await getAvailablePort()
+  } catch {
+    showErrorAndQuit(
+      'Startup Failed',
+      "The app couldn't allocate a local port. Please close other apps and try again.",
+    )
+    return null
+  }
 
   if (isQuitting) {
     return null
@@ -148,15 +176,16 @@ const createWindow = async () => {
   }
 
   if (!ready) {
-    console.error(
+    showErrorAndQuit(
+      'Startup Failed',
       app.isPackaged
-        ? 'Server binary did not start in time.'
+        ? 'The app is taking too long to start. Please try again.'
         : 'Dev server not responding. Run `bun dev` in apps/server first.',
     )
-    app.quit()
     return
   }
 
+  serverReady = true
   mainWindow.loadURL(serverUrl)
 }
 
@@ -170,7 +199,12 @@ app
   .then(createWindow)
   .catch((e) => {
     console.error('Failed to create window:', e)
-    app.quit()
+    showErrorAndQuit(
+      "App Couldn't Start",
+      app.isPackaged
+        ? "We couldn't open the application window. Please restart your computer and try again."
+        : `Failed to create window: ${e instanceof Error ? e.message : String(e)}`,
+    )
   })
 
 app.on('window-all-closed', () => {
@@ -182,7 +216,15 @@ app.on('window-all-closed', () => {
 
 app.on('activate', () => {
   if (!isQuitting && BrowserWindow.getAllWindows().length === 0) {
-    createWindow()
+    createWindow().catch((e) => {
+      console.error('Failed to re-create window:', e)
+      showErrorAndQuit(
+        "App Couldn't Start",
+        app.isPackaged
+          ? "We couldn't open the application window. Please restart the app."
+          : `Failed to re-create window: ${e instanceof Error ? e.message : String(e)}`,
+      )
+    })
   }
 })