fix: preserve season zero semantics (#6150)

tests/test_agent_search_media_tool.py

@@ -0,0 +1,10 @@
+from app.agent.tools.impl.search_media import SearchMediaTool
+
+
+def test_tool_message_displays_special_season_zero():
+    """媒体搜索提示应展示显式季 0。"""
+    tool = SearchMediaTool(session_id="session-1", user_id="10001")
+
+    message = tool.get_tool_message(title="测试剧", media_type="tv", season=0)
+
+    assert "第0季" in message