fix: drop description for simple video creatives — unsettable in Meta API v24

Meta API v24 rejects description in both video_data and
call_to_action.value.link_description (deprecated). The description
parameter is silently ignored for simple video creatives.

Author: nictuku

meta_ads_mcp/core/ads.py

@@ -1080,8 +1080,9 @@ async def create_ad_creative(
                 if headline:
                     video_data["title"] = headline
 
-                if description:
-                    video_data["description"] = description
+                # NOTE: Meta API v24 rejects "description" in video_data AND
+                # "link_description" in call_to_action.value (deprecated).
+                # Description is not settable for simple video creatives.
 
                 # Build call_to_action with the destination URL.
                 # For video creatives, link_url MUST go in call_to_action.value.link

tests/test_video_creatives.py

@@ -72,7 +72,9 @@ async def test_simple_video_creative_uses_video_data():
         assert "link" not in video_data, "link must NOT be in video_data directly"
         assert video_data["message"] == "Check out this video"
         assert video_data["title"] == "Watch Now"
-        assert video_data["description"] == "Amazing content"
+        # description is not settable for simple video creatives (Meta API v24
+        # rejects it in both video_data and call_to_action.value)
+        assert "description" not in video_data
         assert video_data["call_to_action"]["type"] == "LEARN_MORE"
         assert video_data["call_to_action"]["value"]["link"] == "https://example.com/"