Detect and validate app runtime from uploaded archives.

Reject zip uploads when the selected runtime does not match archive contents, and re-validate before Kaniko builds to fail fast instead of producing the wrong Dockerfile.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/lib/errors.ts

@@ -22,6 +22,30 @@ export interface ClassifiedError {
   backendMessage?: string;
 }
 
+export interface RuntimeMismatchPayload {
+  configured: string;
+  detected: string;
+  signals?: string[];
+}
+
+/** Reads structured runtime mismatch fields from a 400 upload response. */
+export function readRuntimeMismatch(err: unknown): RuntimeMismatchPayload | null {
+  if (!axios.isAxiosError(err) || err.response?.status !== 400) return null;
+  const data = err.response.data;
+  if (!data || typeof data !== 'object') return null;
+  const body = data as Record<string, unknown>;
+  if (typeof body.configured === 'string' && typeof body.detected === 'string') {
+    return {
+      configured: body.configured,
+      detected: body.detected,
+      signals: Array.isArray(body.signals)
+        ? body.signals.filter((s): s is string => typeof s === 'string')
+        : undefined,
+    };
+  }
+  return null;
+}
+
 /** Flattens NestJS-style `message: string | string[]` into one string. */
 function readBackendMessage(data: unknown): string | undefined {
   if (!data || typeof data !== 'object') return undefined;