track(merged): feat(images): Unify combined sidecar images, drop client-registration (ext#409)

Tracking stub for **merged PR kagenti-extensions#409** — auto-created so it rolls up as completed work under epic #1568.

https://github.com/kagenti/kagenti-extensions/pull/409

_Closed because the PR is already merged. Label `epic-progress` marks auto-created trackers._