Faces travel to their new Cells on Re-solve

## What to build

The motion, in `afrender`. On Re-solve every Face interpolates from its old Cell to its new one instead of the wall snapping. This is what makes the piece read as a crowd rearranging itself rather than as a slideshow.

Re-solve and Drift are visually distinct motions and must stay that way. Drift is Stage 3, so this is the first of the two and the one that sets what the other has to differ from. Write down what makes it distinct.

The movement penalty in #12 is what makes this animation coherent: Faces should mostly move a little. If everything crosses the wall on every Capture, λ is the dial, not the easing curve.

A Face entering the Window for the first time and a Face leaving it are Stage 3 (ADR-0004). Here, the Window's membership does not change.

## Acceptance criteria

- [ ] On Re-solve, every Face whose Cell changed animates from the old Cell to the new one
- [ ] A Face whose Cell did not change does not move
- [ ] The transition runs at the display's frame rate at the top of the Grid range on the target machine, and the frame time is recorded
- [ ] A Capture landing mid-transition is handled deliberately, and the choice is written down
- [ ] What makes Re-solve visually distinct from Drift is written down before Stage 3 is started

## Blocked by

- #13

This work is blocked by #13 and takes place in afrender. Once the prerequisite is complete, start by tracing Re-solve through the Grid, Face, Cell, and Capture flow; verify unchanged Cells stay still and changed Cells animate at the target display rate. Record the frame time, document the mid-transition Capture choice, and write down how Re-solve differs visually from Drift before Stage 3.

Written by the indexing model from the issue text.