Holding an arrow key on a selection with a fast OS key-repeat rate
crashed the workspace with React error #185 (Maximum update depth
exceeded): each OS key-repeat event was converted 1:1 into a
`set-modifiers`/`set-wasm-modifiers` store write inside
`nudge-selected-shapes` with no throttle, starving the renderer.
The sibling mouse-driven resize/rotate/move paths got an `rx/sample`
throttle in PR #10560; the keyboard-nudge path was the only transform
stream left un-throttled. This change applies the same `rx/sample`
throttle to the nudge stream, mirroring the drag-path structure, and
adds a regression test guarding the final committed position
invariant under a burst of 20 `move-selected` events for both the WASM
and legacy (non-WASM) branches.
Closes#10726
AI-assisted-by: glm-5.2
