panic: get_submission while reserving failed: R(SubmissionNotFound(SubmissionId(u63(7498711361585676288))))

Sentry Issue: [OPSQUEUE-Z](https://channable.sentry.io/issues/7695012195/?referrer=github_integration)

```
panic: get_submission while reserving failed: R(SubmissionNotFound(SubmissionId(u63(7498711361585676288))))
?, in opsqueue::consumer::dispatcher::Dispatcher::join_chunk_with_submission_info::::{closure#0}
?, in opsqueue::consumer::server::state::ConsumerState::fetch_and_reserve_chunks::{closure#0}::{closure#0}
?, in opsqueue::consumer::server::ws_accept_handler::{closure#0}::{closure#0}::{closure#0}
...
(19 additional frame(s) were not displayed)
```

Start with opsqueue::consumer::dispatcher::Dispatcher::join_chunk_with_submission_info and follow its callers in ConsumerState::fetch_and_reserve_chunks and ws_accept_handler. Use the linked Sentry issue to investigate why reserving encounters SubmissionNotFound; done means the reported panic is resolved and the behavior is verified against the failure path.

Rédigé par le modèle d'indexation à partir du texte de l'issue.