Bug: Race Module Metadata Mismatch Breaks Combine Logic

> ### Bug: Race Module Metadata Mismatch Breaks Combine Logic
> The combine completion handler in `interaction.service.ts` is unreachable because the metadata properties it checks are incorrectly set. The handler requires `isCombineGeneration` and `combineSourceInteractionId` to be present in the interaction's metadata. However, the race module sets `isCompactGeneration: true` and `targetUserInteractionId` instead. This mismatch prevents the combine completion logic from executing, breaking the race combining functionality.
>
> `src/services/interaction.service.ts#L1192-L1247`
> https://github.com/DimitriGilbert/LiteChat/blob/2ce2a25913ce0eed69ae9fd4f6093685f55c7ff9/src/services/interaction.service.ts#L1192-L1247

from bugbot, it is a future me problem, the feature works.