Steadier AI image generation, CLI long-task status, cleaner task view

AI Image Generation
- Image generation is more reliable: when the primary image provider rejects a request, generation now automatically falls back to the backup model instead of failing the whole request, so a single upstream hiccup no longer blocks your image.
Long-running Tasks (CLI)
- You can now list and check the status of long-running jobs (video, 3D, speech) from the Kollab command line; status and watch now return results instead of being blocked.
Task View
- Artifact thumbnails look cleaner, and a long-running task's status now collapses to a single tidy line so the task view is easier to scan.