Repair object-shaped children maps into arrays in page specs

Why: Live E2E on the dev instance - the model keyed section children
as an object map (children.item.*), the strict decode rejected it, and
the page fell back to a file artifact; the guidance fix made the model
call present, this closes the remaining shape gap.

Evidence: genui suite green incl. the reproduction case; post-deploy
E2E rerun recorded in the Dev task.

Impact: Repair strategy only; validation unchanged.

Refs: Dev task fix/genui-page-visibility (E2E follow-up)

internal/genui/genui.go

@@ -274,10 +274,53 @@ func normalizeSpecParam(v any) any {
 			}
 		}
 	}
+	repairChildrenShape(m)
 	repairPairs(m)
 	return m
 }
 
+// repairChildrenShape 递归修复 children 的常见形状偏差（真实模型实测）：
+// children 为对象（按 key 编号的子节点映射）→ 取其值转数组；单对象 → 包一层数组。
+func repairChildrenShape(node any) {
+	m, ok := node.(map[string]any)
+	if !ok {
+		return
+	}
+	if ch, ok := m["children"]; ok && ch != nil {
+		switch v := ch.(type) {
+		case map[string]any:
+			arr := make([]any, 0, len(v))
+			for _, val := range v {
+				arr = append(arr, val)
+			}
+			m["children"] = arr
+		case []any:
+			for _, c := range v {
+				if cm, ok := c.(map[string]any); ok {
+					repairChildrenShape(cm)
+				}
+			}
+		default:
+			// 单对象子节点
+			if cm, ok := ch.(map[string]any); ok {
+				m["children"] = []any{cm}
+			}
+		}
+	}
+	for _, v := range m {
+		if vm, ok := v.(map[string]any); ok {
+			repairChildrenShape(vm)
+		}
+		if va, ok := v.([]any); ok {
+			for _, item := range va {
+				if im, ok := item.(map[string]any); ok {
+					repairChildrenShape(im)
+				}
+			}
+		}
+	}
+}
+
 // repairPairs 递归把 "kv"/"cells" 下的对象项改写为二元组。
 func repairPairs(node any) {
 	m, ok := node.(map[string]any)

internal/genui/genui_test.go

@@ -280,3 +280,19 @@ type ledgerHost struct {
 
 func (h *ledgerHost) KVPut(key, value string) error               { h.kv[key] = value; return nil }
 func (h *ledgerHost) Audit(action, target, evidence string) error { return nil }
+
+func TestNormalizeChildrenShape(t *testing.T) {
+	// 真实偏差（2026-10-11 dev 实测）：模型把 children 写成按 key 编号的对象映射。
+	in := map[string]any{
+		"type": "section", "id": "n1", "title": "结论",
+		"children": map[string]any{
+			"item": map[string]any{"type": "markdown", "id": "m1", "markdown": "结论先行"},
+		},
+	}
+	out := normalizeSpecParam(map[string]any{"title": "t", "nodes": []any{in}})
+	nodes := out.(map[string]any)["nodes"].([]any)
+	ch := nodes[0].(map[string]any)["children"].([]any)
+	if len(ch) != 1 || ch[0].(map[string]any)["id"] != "m1" {
+		t.Fatalf("children should be repaired to array, got %v", ch)
+	}
+}