fix(site-import): GEN2 嵌套分组展平容错 + 提示词钉死扁平输出（Task10 实测 glm-4-flash 常见形态）

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

tests/test_site_import_generator.py

@@ -432,3 +432,33 @@ class TestCrawlWarningsMerge:
         draft = generator.build(gen, ANALYSIS_JSON, crawl, SOURCE_TEXT)
         assert "logo 为不支持的格式，已跳过" in draft["warnings"]
         assert "子页过薄已跳过：/thin" in draft["warnings"]
+
+
+class TestNestedFlatten:
+    def test_嵌套分组自动展平(self):
+        """Task 10 实测：glm-4-flash 常把键按模板分组嵌套——展平容错。"""
+        from app.platform.site_import.generator import _flatten_nested
+        nested = {"system": {"身份描述": "x", "产品统称": "y"},
+                  "extractor": {"采购域": "z"}, "brand_title": "T"}
+        flat = _flatten_nested(nested)
+        assert flat == {"身份描述": "x", "产品统称": "y", "采购域": "z", "brand_title": "T"}
+
+    def test_本来就扁平原样返回(self):
+        from app.platform.site_import.generator import _flatten_nested
+        flat_in = {"身份描述": "x", "brand_title": "T"}
+        assert _flatten_nested(dict(flat_in)) == flat_in
+
+    def test_非dict子值不展平(self):
+        from app.platform.site_import.generator import _flatten_nested
+        weird = {"a": "字符串", "b": {"身份描述": "x"}}
+        assert _flatten_nested(weird) is weird or _flatten_nested(weird) == weird
+
+    async def test_generate接受嵌套输出(self):
+        """端到端：fake 回嵌套 JSON 也能过 generate。"""
+        import json as _json
+        nested = {"system": {"身份描述": "x"}, "brand_title": "T"}
+        class NestedP:
+            async def chat(self, m, s):
+                return "```json\n" + _json.dumps(nested, ensure_ascii=False) + "\n```"
+        out = await generator.generate(NestedP(), ANALYSIS_JSON)
+        assert out.get("身份描述") == "x" and out.get("brand_title") == "T"