fix(runner): Dev-Neustart bei geänderten Variablen, Liveness-Prüfung, npm-ci-Fallback

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

runner/src/proxy.js

@@ -83,7 +83,8 @@ export function createProxy({ config, dev, request = http.request, upstreamTimeo
       });
       let timedOut = false;
       up.setTimeout(upstreamTimeoutMs, () => { timedOut = true; up.destroy(); });
-      up.on('error', () => {
+      up.on('error', (err) => {
+        if (['ECONNREFUSED', 'ENOTFOUND', 'EHOSTUNREACH', 'EAI_AGAIN'].includes(err?.code)) dev.markDead?.(sub)?.catch?.(() => {});
         if (!res.headersSent) {
           const body = timedOut ? 'Die Preview antwortet nicht rechtzeitig (504).' : 'Die Preview ist gerade nicht erreichbar (502).';
           res.writeHead(timedOut ? 504 : 502, { 'Content-Type': 'text/plain; charset=utf-8', 'Content-Length': Buffer.byteLength(body) });