Avoid double-stepping tvOS remote navigation

[adamtheturtle]

Only handle onMoveCommand when focus is on the search field. Closes #137

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Note

Low Risk
Small tvOS-only navigation guard; no auth, data, or API changes. One-line control-flow fix with a clear comment.

Overview
Stops Siri Remote / game-controller list navigation from skipping a row on tvOS.

onMoveCommand now only calls move(by:) when focus is still on the search field (focusedResultID == nil). Once a result row is focused, the focus engine plus onChange(of: focusedResultID) already update selectedIndex, so the extra move was double-stepping.

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