Generate an AI image revision.

Generate a variation of an existing image (or a captured video frame) guided by a free-text prompt. The result is staged as a temporary Scratch upload — call `POST /scratch/{id}/promote` to turn the chosen revision into a real asset on the destination project (there is no `/ai/revisions/promote` route). `source` must contain exactly one of `url` (public media URL), `scratchId` (an upload created via `POST /ai/revisions/source-upload` — the preferred path for video frames; it must belong to the caller and workspace and still be active), or `dataUrl` (deprecated legacy path for video frames). Requires `canAiGenerateImageRevision` on the workspace, an active subscription, the `ai` capability, the `aiImageRevisionEnabled` workspace/project setting (`aiImageRevisionAllowReviewer` for reviewers) and a worst-case credit pre-check (a flat estimate).

curl -X POST "https://example.com/ai/revisions" \  -H "Content-Type: application/json" \  -d '{    "workspaceId": "ef0efa32-d1c1-43d4-a5e2-fe7b4f00403c",    "source": {},    "prompt": "string"  }'

{  "revisionId": "bae12d01-48af-47b3-9304-b09ef0081cd6",  "revisionUrl": "string",  "model": "string",  "quality": "string",  "billedCredits": 0,  "balanceAfter": 0,  "eventId": "d6703cc8-9e79-415d-ac03-a4dc7f6ab43c"}