feat(scripts): PoC 阶段 1 - CLI + Layer00619 BackHall 端到端跑通

- scripts/legacy-layer-to-cocos-prefab-cli.mjs (CLI 入口: <inputXml> [<youlePrefab>] <outputDir>)
- framework-tests/legacy-layer-migration/poc-iconbutton.test.mjs (1 个 node:test 端到端校验 cc.Prefab 头 + group-55 父节点)
- YouleNexus/out/legacy-migration/BackHall_Layer.prefab (生成产物, 437 lines)
- YouleNexus/out/legacy-migration/BackHall_Layer.prefab.diff (vs YouleNexus Layer619_BackOtherGame.prefab, 1244 lines)

累计: 30/30 PASS (29 prior + 1 PoC). Layer00619 (1 Spirit, type=3 ProgressBar, group=55) 是最简 PoC, diff 大是预期 (脚本首个端到端输出 vs 手写 prefab 必然差异大).

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

cocoscreator_projects/framework-tests/legacy-layer-migration/poc-iconbutton.test.mjs

@@ -0,0 +1,31 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { execSync } from 'node:child_process';
+import { existsSync, readFileSync } from 'node:fs';
+
+// PoC 阶段 1 端到端: Layer00619 BackHall_Layer (1 Spirit, type=3 ProgressBar) →
+// prefab JSON + (diff, if any) → 关键字段校验.
+//
+// 注: 原 brief 建议 IconButton, 但 IconButton 无对应 Layer; spec 改用 BackHall_Layer
+// 作为最简 1-Spirit PoC. Target YouleNexus prefab 不存在时 CLI 仅生成 prefab, 不报错.
+//
+// 路径从 cocoscreator_projects/ 运行 (与其他 legacy-layer-migration 测试一致).
+const CLI = 'node scripts/legacy-layer-to-cocos-prefab-cli.mjs';
+const INPUT = '../projects/Game_Surface_3/save/Layer00619.xml';
+const TARGET = 'YouleNexus/assets/framework/ui/prefabs/widgets/Layer619_BackOtherGame.prefab';
+const OUTPUT_DIR = 'YouleNexus/out/legacy-migration/';
+const OUTPUT = 'YouleNexus/out/legacy-migration/BackHall_Layer.prefab';
+
+test('Layer00619 端到端生成 + 校验关键字段', () => {
+  execSync(`${CLI} ${INPUT} ${TARGET} ${OUTPUT_DIR}`, { stdio: 'pipe' });
+
+  assert.ok(existsSync(OUTPUT), `${OUTPUT} 应生成`);
+  const json = JSON.parse(readFileSync(OUTPUT, 'utf8'));
+  assert.ok(Array.isArray(json));
+  assert.equal(json[0].__type__, 'cc.Prefab');
+  assert.equal(json[0]._name, 'BackHall_Layer');
+
+  // 校验含 group-55 父节点 (BackHall_Layer.xml Spirit BelongGroupID=55).
+  const groupNode = json.find(o => o.__type__ === 'cc.Node' && o._name === 'group-55');
+  assert.ok(groupNode, '应有 group-55 父节点');
+});