/calendar中item的summary值始终为空

```json
{
"id": 899,
"url": "http://bgm.tv/subject/899",
"type": 2,
"name": "名探偵コナン",
"name_cn": "名侦探柯南",
"summary": "",
"air_date": "1996-01-08",
"air_weekday": 1,
"rating": {
"total": 6357,
"count": {
"1": 17,
"2": 6,
"3": 16,
"4": 41,
"5": 198,
"6": 738,
"7": 1942,
"8": 1906,
"9": 750,
"10": 743
},
"score": 7.7
},
"rank": 582,
"images": {
"large": "http://lain.bgm.tv/pic/cover/l/01/88/899_Q3F3X.jpg",
"common": "http://lain.bgm.tv/pic/cover/c/01/88/899_Q3F3X.jpg",
"medium": "http://lain.bgm.tv/pic/cover/m/01/88/899_Q3F3X.jpg",
"small": "http://lain.bgm.tv/pic/cover/s/01/88/899_Q3F3X.jpg",
"grid": "http://lain.bgm.tv/pic/cover/g/01/88/899_Q3F3X.jpg"
},
"collection": {
"doing": 5689
}
}
```

Start by reproducing the /calendar response for item 899 and compare its empty summary with the source subject data. Trace the /calendar endpoint to where item fields are assembled; done means the response includes the expected summary value and a regression test covers it.

Written by the indexing model from the issue text.