translator: enqueue should return the job ids it created

Read against **0.10.1**.

## Problem

`enqueue` returns `{ success, queued: N }`. It does not return the ids of the jobs it created.

A host that wants to cancel a run later therefore has nothing to store. The only way to get an id is
`get-document-status` (`/translate/document/:slug/:id`), which returns the latest job per target
locale — so cancelling means an extra lookup at cancel time, on a shape that reflects "latest" rather
than "the job I created".

Combined with the absence of run context in callbacks (#110), it means a host cannot durably connect an editor's
action to a specific job at all.

## Why this matters

We store one row per document × target locale for editorial state and would naturally record the job
id on it at enqueue. We cannot, so cancel does a `findByCollection` lookup first — and that call has
its own scaling problem (#108: it loads every job unpaginated on every enqueue).

## Suggested shape

Return the created job ids, keyed by target locale:

```js
{ success: true, queued: 3, jobs: { fr: "…", de: "…", it: "…" } }
```

The ids exist at that point; they are just not returned.

Start at the translator enqueue path and trace where the created job records are collected and where the current { success, queued } response is assembled. Compare it with get-document-status at /translate/document/:slug/:id, then verify that enqueue returns the created ids keyed by target locale while preserving success and queued.

Written by the indexing model from the issue text.