fix(feishu): parse post wrapper payload for rich text messages

tests/test_feishu_post_content.py

@@ -0,0 +1,40 @@
+from nanobot.channels.feishu import _extract_post_content
+
+
+def test_extract_post_content_supports_post_wrapper_shape() -> None:
+    payload = {
+        "post": {
+            "zh_cn": {
+                "title": "日报",
+                "content": [
+                    [
+                        {"tag": "text", "text": "完成"},
+                        {"tag": "img", "image_key": "img_1"},
+                    ]
+                ],
+            }
+        }
+    }
+
+    text, image_keys = _extract_post_content(payload)
+
+    assert text == "日报 完成"
+    assert image_keys == ["img_1"]
+
+
+def test_extract_post_content_keeps_direct_shape_behavior() -> None:
+    payload = {
+        "title": "Daily",
+        "content": [
+            [
+                {"tag": "text", "text": "report"},
+                {"tag": "img", "image_key": "img_a"},
+                {"tag": "img", "image_key": "img_b"},
+            ]
+        ],
+    }
+
+    text, image_keys = _extract_post_content(payload)
+
+    assert text == "Daily report"
+    assert image_keys == ["img_a", "img_b"]