fix(preview): zombie process cleanup on anatomy load

vibn-frontend/app/api/projects/[projectId]/anatomy/route.ts

@@ -792,7 +792,60 @@ async function loadPreviews(projectId: string): Promise<Preview[]> {
         WHERE project_id = $1 AND state != 'stopped'`,
       [projectId],
     );
-    return sortDevPreviewsFrontendFirst(rows).map((r) => ({
+
+    // Filter out zombies: if a server is marked 'running' but the URL returns a 50x
+    // Gateway error or times out, the process died. We mark it stopped so the
+    // UI can trigger an auto-restart.
+    const activePreviews: typeof rows = [];
+
+    await Promise.all(
+      rows.map(async (r) => {
+        if (r.state !== "running") {
+          activePreviews.push(r);
+          return;
+        }
+
+        try {
+          const controller = new AbortController();
+          const timeout = setTimeout(() => controller.abort(), 2500); // Fast 2.5s timeout
+          const ping = await fetch(r.preview_url, {
+            method: "HEAD",
+            signal: controller.signal,
+          });
+          clearTimeout(timeout);
+
+          // 502/503/504 means Traefik is up but the container isn't answering.
+          // 404 means Traefik doesn't even know about the route.
+          if (
+            ping.status === 502 ||
+            ping.status === 503 ||
+            ping.status === 504 ||
+            ping.status === 404
+          ) {
+            console.warn(
+              `[anatomy] Preview zombie detected for ${r.preview_url} (HTTP ${ping.status}). Marking stopped.`,
+            );
+            await query(
+              `UPDATE fs_dev_servers SET state = 'stopped' WHERE id = $1`,
+              [r.id],
+            ).catch(() => {});
+          } else {
+            activePreviews.push(r);
+          }
+        } catch (e: any) {
+          // If the fetch completely fails (e.g. timeout, DNS failure), it's dead.
+          console.warn(
+            `[anatomy] Preview zombie detected for ${r.preview_url} (${e.message}). Marking stopped.`,
+          );
+          await query(
+            `UPDATE fs_dev_servers SET state = 'stopped' WHERE id = $1`,
+            [r.id],
+          ).catch(() => {});
+        }
+      }),
+    );
+
+    return sortDevPreviewsFrontendFirst(activePreviews).map((r) => ({
       id: r.id,
       name: r.name,
       command: r.command ?? undefined,