Auto-download Go binary on startup and validate setup

The postinstall script doesn't run on toes (package.json is
transformed during deploy), so the binary was never downloaded.
Now the server downloads it from GitHub releases if missing.
Added validate() to catch missing DATA_DIR and non-executable
binary with clear error messages.

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

src/server.ts

@@ -1,10 +1,10 @@
 import { join } from 'path'
-import { unlinkSync } from 'fs'
+import { accessSync, chmodSync, constants, mkdirSync, unlinkSync } from 'fs'
 import type { ServerWebSocket, Subprocess } from 'bun'
 
-const DATA_DIR = process.env.DATA_DIR!
+const DATA_DIR = process.env.DATA_DIR
 const PORT = Number(process.env.PORT) || 3000
-const SOCKET_PATH = join(DATA_DIR, 'tronbyt.sock')
+const SOCKET_PATH = DATA_DIR ? join(DATA_DIR, 'tronbyt.sock') : ''
 const BIN_DIR = join(import.meta.dir, '..', 'bin')
 
 let goProcess: Subprocess | undefined
@@ -107,13 +107,52 @@ async function waitForHealthy(maxAttempts = 60): Promise<boolean> {
   return false
 }
 
+async function downloadBinary(binPath: string): Promise<boolean> {
+  const name = getBinaryName()
+  const url = `https://github.com/tronbyt/server/releases/latest/download/${name}`
+
+  console.log(`Downloading ${name}...`)
+  try {
+    const resp = await fetch(url, { redirect: 'follow' })
+    if (!resp.ok) {
+      console.error(`Download failed: ${resp.status} ${resp.statusText}`)
+      return false
+    }
+
+    mkdirSync(BIN_DIR, { recursive: true })
+    await Bun.write(binPath, resp)
+
+    chmodSync(binPath, 0o755)
+
+    console.log('Download complete')
+    return true
+  } catch (e) {
+    console.error('Download failed:', e)
+    return false
+  }
+}
+
+function validate(): string | undefined {
+  if (!DATA_DIR) return 'DATA_DIR env var is not set — toes should provide this automatically'
+
+  const binPath = join(BIN_DIR, getBinaryName())
+  try {
+    accessSync(binPath, constants.X_OK)
+  } catch {
+    return `Binary not found or not executable: ${binPath}`
+  }
+}
+
 async function spawnGoServer() {
   const binPath = join(BIN_DIR, getBinaryName())
 
   if (!(await Bun.file(binPath).exists())) {
-    console.error(`Binary not found: ${binPath}`)
+    if (!(await downloadBinary(binPath))) return
-    console.error(`Download from https://github.com/tronbyt/server/releases`)
+  }
-    console.error(`Expected: ${getBinaryName()}`)
+
+  const error = validate()
+  if (error) {
+    console.error(`Setup error: ${error}`)
     return
   }
 
@@ -126,7 +165,7 @@ async function spawnGoServer() {
       ...process.env,
       TRONBYT_UNIX_SOCKET: SOCKET_PATH,
       DATA_DIR,
-      DB_DSN: join(DATA_DIR, 'tronbyt.db'),
+      DB_DSN: join(DATA_DIR!, 'tronbyt.db'),
       PRODUCTION: process.env.PRODUCTION ?? 'false',
       SINGLE_USER_AUTO_LOGIN: process.env.SINGLE_USER_AUTO_LOGIN ?? 'true',
       SYSTEM_APPS_AUTO_REFRESH: process.env.SYSTEM_APPS_AUTO_REFRESH ?? 'true',