Bugfix: Remove wrong artifact cache override; add a note on system st…

…art time… (#98)

* Remove wrong artifact cache override in `flashdreams_managed.yaml`
* Add a note on system start timeout in the initial run in
`docs/VIDEO_MODEL.md`

Sync from GitLab (April 2026 - full sync) (#73)

This commit brings the GitHub repository up to date with the internal
GitLab repository as of April 20, 2026. This puts all github files in
the same state as the internal repo.

Changes include:
- Latest feature updates and bug fixes from internal development
- Updated documentation and configuration files
- All recent improvements to runtime, eval, driver, and other components
External contributions (PRs in github) were previously cherry-picked to
GitLab and are included in this sync.

Future syncs will follow a monthly release process to keep the public
repository aligned with internal development while preserving external
contributions.