feat(feishu): render markdown replies as cards

tests/test_feishu_static_card.py

@@ -0,0 +1,34 @@
+import json
+
+from channel.feishu.feishu_static_card import build_text_delivery, contains_markdown
+
+
+def test_plain_text_keeps_native_feishu_text_message():
+    msg_type, content = build_text_delivery("hello from CowAgent")
+
+    assert msg_type == "text"
+    assert json.loads(content) == {"text": "hello from CowAgent"}
+
+
+def test_markdown_reply_uses_card_2_markdown_element():
+    msg_type, content = build_text_delivery("**Build complete**\n\n- tests passed")
+
+    card = json.loads(content)
+    assert msg_type == "interactive"
+    assert card["schema"] == "2.0"
+    assert card["body"]["elements"] == [
+        {"tag": "markdown", "content": "**Build complete**\n\n- tests passed"}
+    ]
+
+
+def test_markdown_cards_can_be_disabled():
+    msg_type, content = build_text_delivery("# Status", enabled=False)
+
+    assert msg_type == "text"
+    assert json.loads(content) == {"text": "# Status"}
+
+
+def test_markdown_detection_avoids_common_plain_text_punctuation():
+    assert contains_markdown("release 1.2.0 - all checks passed") is False
+    assert contains_markdown("Use `cow --help` for details") is True
+    assert contains_markdown("| Item | State |\n| --- | --- |\n| API | ready |") is True