docs(api): mark collection responses nullable (#6430)

* docs(api): mark collection responses nullable

Describe allLinks and panel log response objects as nullable string arrays so generated clients accept the existing nil-slice wire format. Pin both schemas with buildSpec regression assertions and regenerate the OpenAPI copies.

* docs(api): include nullable Xray log responses

Allow generated response arrays to opt into nullability while retaining their schema references and Go-derived examples. Apply this to Xray logs, whose nil slices already serialize as null, and pin the schema and example through buildSpec.

frontend/scripts/build-openapi.mjs

@@ -245,7 +245,13 @@ function buildOperation(ep, tag) {
       );
     }
     const ref = { $ref: `#/components/schemas/${ep.responseSchema}` };
-    objSchema = ep.responseSchemaArray ? { type: 'array', items: ref } : ref;
+    objSchema = ep.responseSchemaArray
+      ? {
+          type: 'array',
+          ...(ep.responseSchemaArrayNullable ? { nullable: true } : {}),
+          items: ref,
+        }
+      : ref;
     if (successExample === undefined) {
       successExample = { success: true, obj: ep.responseSchemaArray ? [obj] : obj };
     }