feat(web): highlight the offending field on a set_fields 422 (#28)

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

web/src/api/queries.ts

@@ -10,6 +10,13 @@ export class HttpError extends Error {
   }
 }
 
+export class FieldRejection extends Error {
+  constructor(public readonly field: string, public readonly code: string) {
+    super(`field rejected: ${field}`);
+    this.name = "FieldRejection";
+  }
+}
+
 type UserView = components["schemas"]["UserView"];
 type LoginRequest = components["schemas"]["LoginRequest"];
 
@@ -179,12 +186,19 @@ export function useSetFields() {
 
   return useMutation({
     mutationFn: async ({ id, fields }: { id: string; fields: Record<string, unknown> }) => {
-      const { response } = await api.PUT("/api/admin/objects/{id}/fields", {
+      const { response, error } = await api.PUT("/api/admin/objects/{id}/fields", {
         params: { path: { id } },
         body: fields as Record<string, never>,
       });
 
-      if (response.status !== 204) throw new Error("set fields failed");
+      if (response.status === 204) return;
+
+      if (response.status === 422 && error && typeof error === "object" && "field" in error) {
+        const detail = error as { field: string; code: string };
+        throw new FieldRejection(detail.field, detail.code);
+      }
+
+      throw new Error("set fields failed");
     },
     onSuccess: (_d, { id }) => {
       void qc.invalidateQueries({ queryKey: ["object", id] });