Preserve deterministic testimonial selector layout

## Problem
The Home testimonial selector retains its portraits and copy but loses the source runtime positioning. Candidate portraits align from the left while the source selector group is centered, producing four dominant mismatch regions.

## Direction
Fold deterministic selector/carousel presentation into generic editable block geometry or preserve the required bounded runtime behavior.

## Acceptance
- Testimonial portraits match source positions and selected state.
- Content remains editable and editor-valid.
- Repeated captures are deterministic.
- Transformer contracts and parity fixtures pass.

## AI assistance
OpenAI gpt-5.6-sol through OpenCode analyzed the parity evidence and drafted this issue. Chris Huber remains responsible for scope and implementation decisions.

Start with the Home testimonial selector and the generic editable block geometry or bounded runtime behavior described in the issue. Compare candidate portrait positions and selected state with the source selector, then verify that content remains editable and repeated captures are deterministic. Run the transformer contracts and parity fixtures to confirm the acceptance criteria.

Written by the indexing model from the issue text.