Cannot use @connection on fragment

Using @connection on a fragment does not work:

TickerEventListWrapper.js
```
fragment TickerEventListWrapper_item on Ticker {
events(first: 10) {
...TickerEventList_items
}
}
```

TickerEventList.js
```
fragment TickerEventList_items on TickerEventConnection @connection(
key: "TickerEventList_items_events",
) {
edges {
node {
...TickerEvent_item
}
}
}
```

TickerEvent.js
```
fragment TickerEvent_item on TickerEvent {
id
}
```

Using @connection on `events(first: 10)` does also not work because it requires an `edges` key as an immediate child.

Reproduce the example from TickerEventListWrapper.js, TickerEventList.js, and TickerEvent.js, starting with the fragment-level @connection usage and the immediate edges requirement. Trace Relay's handling of these fragments to determine the expected behavior and verify the reported failure.

Written by the indexing model from the issue text.