Add swipe-to-dismiss gesture for mobile stat block drawer

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/hooks/use-swipe-to-dismiss.ts

@@ -0,0 +1,72 @@
+import { useCallback, useRef, useState } from "react";
+
+const DISMISS_THRESHOLD = 0.35;
+const VELOCITY_THRESHOLD = 0.5;
+
+interface SwipeState {
+	offsetX: number;
+	isSwiping: boolean;
+}
+
+export function useSwipeToDismiss(onDismiss: () => void) {
+	const [swipe, setSwipe] = useState<SwipeState>({
+		offsetX: 0,
+		isSwiping: false,
+	});
+	const startX = useRef(0);
+	const startY = useRef(0);
+	const startTime = useRef(0);
+	const panelWidth = useRef(0);
+	const directionLocked = useRef<"horizontal" | "vertical" | null>(null);
+
+	const onTouchStart = useCallback((e: React.TouchEvent) => {
+		const touch = e.touches[0];
+		startX.current = touch.clientX;
+		startY.current = touch.clientY;
+		startTime.current = Date.now();
+		directionLocked.current = null;
+		const el = e.currentTarget as HTMLElement;
+		panelWidth.current = el.getBoundingClientRect().width;
+	}, []);
+
+	const onTouchMove = useCallback((e: React.TouchEvent) => {
+		const touch = e.touches[0];
+		const dx = touch.clientX - startX.current;
+		const dy = touch.clientY - startY.current;
+
+		if (!directionLocked.current) {
+			if (Math.abs(dx) < 10 && Math.abs(dy) < 10) return;
+			directionLocked.current =
+				Math.abs(dx) > Math.abs(dy) ? "horizontal" : "vertical";
+		}
+
+		if (directionLocked.current === "vertical") return;
+
+		const clampedX = Math.max(0, dx);
+		setSwipe({ offsetX: clampedX, isSwiping: true });
+	}, []);
+
+	const onTouchEnd = useCallback(() => {
+		if (directionLocked.current !== "horizontal") {
+			setSwipe({ offsetX: 0, isSwiping: false });
+			return;
+		}
+
+		const elapsed = (Date.now() - startTime.current) / 1000;
+		const velocity = swipe.offsetX / elapsed / panelWidth.current;
+		const ratio =
+			panelWidth.current > 0 ? swipe.offsetX / panelWidth.current : 0;
+
+		if (ratio > DISMISS_THRESHOLD || velocity > VELOCITY_THRESHOLD) {
+			onDismiss();
+		}
+
+		setSwipe({ offsetX: 0, isSwiping: false });
+	}, [swipe.offsetX, onDismiss]);
+
+	return {
+		offsetX: swipe.offsetX,
+		isSwiping: swipe.isSwiping,
+		handlers: { onTouchStart, onTouchMove, onTouchEnd },
+	};
+}