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Task #5: Add RightClickHighlightTimer(1.5 s) so destination highlights auto-despawn after 1.5 s. Existing clear-on-state-change and clear-on-pause logic still fires early when a move is made or the game is paused. Three unit tests cover timer countdown behaviour. Task #6: Add HintVisualEvent emitted on H key. Source card gets HintHighlight + HintHighlightTimer(2 s) for a yellow glow. Destination PileMarker gets HintPileHighlight with a gold tint (Color::srgb(1.0, 0.85, 0.1)) that restores the original colour when the 2 s timer expires. Five unit tests cover timer expiry and colour invariants. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>