fix(dev server): fall forward from port 1355 without portless

scripts/start-dev.js

@@ -1,6 +1,7 @@
 import { existsSync } from 'node:fs';
 import { join } from 'node:path';
 import { spawn } from 'node:child_process';
+import { resolvePort } from './dev-server-utils.mjs';
 
 const isWindows = process.platform === 'win32';
 const usePortless = process.env.PORTLESS !== '0' && !isWindows;
@@ -8,15 +9,30 @@ const binDir = join(process.cwd(), 'node_modules', '.bin');
 const executableSuffix = isWindows ? '.cmd' : '';
 const portlessBin = join(binDir, `portless${executableSuffix}`);
 const viteBin = join(binDir, `vite${executableSuffix}`);
+const fallbackHost = '127.0.0.1';
+const fallbackUrlHost = '5chan.localhost';
+const fallbackRequestedPort = 1355;
 
 const command = usePortless && existsSync(portlessBin) ? portlessBin : viteBin;
-const args =
-  command === portlessBin
-    ? ['5chan', 'vite']
-    : ['--host', '5chan.localhost', '--port', '1355', '--strictPort'];
+let args;
 
-if (command !== portlessBin && process.env.PORTLESS !== '0') {
-  console.warn('portless unavailable on this platform, using vite directly on http://5chan.localhost:1355');
+if (command === portlessBin) {
+  args = ['5chan', 'vite'];
+} else {
+  const port = await resolvePort(fallbackRequestedPort);
+  const fallbackUrl = `http://${fallbackUrlHost}:${port}`;
+
+  args = ['--host', fallbackHost, '--port', String(port), '--strictPort'];
+
+  if (command !== portlessBin && process.env.PORTLESS !== '0') {
+    console.warn(`portless unavailable on this platform, using vite directly on ${fallbackUrl}`);
+  } else {
+    console.log(`Starting Vite directly at ${fallbackUrl}`);
+  }
+
+  if (port !== fallbackRequestedPort) {
+    console.log(`Preferred port ${fallbackRequestedPort} is busy, so this run will use ${fallbackUrl}.`);
+  }
 }
 
 const child = spawn(command, args, {
@@ -32,4 +48,3 @@ child.on('exit', (code, signal) => {
 
   process.exit(code ?? 0);
 });
-