Radius slider floods the undo stack with one entry per pointer move

[mehdibha]

ValueSlider in www/src/modules/create/panel/primitives.tsx commits through a continuous onChange with no commit-on-release. Every intermediate value is a separate ?preset= navigation, and usePresetHistory records each one.

Failure: dragging the Radius slider (step 0.05) writes dozens of history entries; undo then steps back one increment per click instead of undoing the drag. It also costs one router navigation plus a preset re-encode per pointer move.

Fix direction: commit on onChangeEnd and keep onChange for local visual state.

Found reviewing #511.