feat(space): 나가기 버튼 롱프레스 가속 진행 인터랙션 추가

맥락:

- /space에서 실수 이탈을 줄이면서도 명확한 탈출 동선을 유지하기 위해 나가기 액션을 1초 롱프레스 방식으로 변경

변경사항:

- features/exit-hold 추가(useHoldToConfirm, ExitHoldButton)

- 1초 롱프레스와 가속 진행 규칙(0.05초 -> 20%)을 feature 내부에 구현

- 몰입 OFF에서는 bar(좌->우 fill), 몰입 ON에서는 ring 진행 표시로 분기

- 1초 미만 해제/마우스 leave/touch cancel 시 진행률 즉시 리셋

- 완료 시 나가기(더미) 토스트 + 몰입 모드 OFF 동작 연결

- docs/90_current_state.md, docs/session_brief.md 상태 업데이트

검증:

- npx tsc --noEmit

세션-상태: 상단 나가기 액션은 롱프레스 완료 시에만 트리거됨

세션-다음: 롱프레스 인터랙션 인지성 보완용 힌트 카피 도입 여부 검토

세션-리스크: 터치 환경에서 롱프레스 UI 의도를 즉시 이해하지 못할 가능성 있음

src/features/exit-hold/index.ts

@@ -0,0 +1 @@
+export * from './ui/ExitHoldButton';

src/features/exit-hold/model/useHoldToConfirm.ts

@@ -0,0 +1,91 @@
+'use client';
+
+import { useRef, useState } from 'react';
+
+const HOLD_DURATION_MS = 1000;
+const BOOST_DURATION_MS = 50;
+
+const mapProgress = (elapsedMs: number) => {
+  if (elapsedMs <= 0) {
+    return 0;
+  }
+
+  if (elapsedMs <= BOOST_DURATION_MS) {
+    return 0.2 * (elapsedMs / BOOST_DURATION_MS);
+  }
+
+  const tailElapsedMs = Math.min(elapsedMs - BOOST_DURATION_MS, HOLD_DURATION_MS - BOOST_DURATION_MS);
+  return 0.2 + 0.8 * (tailElapsedMs / (HOLD_DURATION_MS - BOOST_DURATION_MS));
+};
+
+export const useHoldToConfirm = (onConfirm: () => void) => {
+  const frameRef = useRef<number | null>(null);
+  const startRef = useRef<number | null>(null);
+  const confirmedRef = useRef(false);
+  const [progress, setProgress] = useState(0);
+  const [isHolding, setHolding] = useState(false);
+
+  const clearFrame = () => {
+    if (frameRef.current !== null) {
+      window.cancelAnimationFrame(frameRef.current);
+      frameRef.current = null;
+    }
+  };
+
+  const reset = () => {
+    clearFrame();
+    startRef.current = null;
+    confirmedRef.current = false;
+    setHolding(false);
+    setProgress(0);
+  };
+
+  const step = () => {
+    if (startRef.current === null) {
+      return;
+    }
+
+    const elapsedMs = performance.now() - startRef.current;
+    const nextProgress = mapProgress(elapsedMs);
+    const clampedProgress = Math.min(nextProgress, 1);
+    setProgress(clampedProgress);
+
+    if (clampedProgress >= 1 && !confirmedRef.current) {
+      confirmedRef.current = true;
+      onConfirm();
+      window.setTimeout(() => {
+        reset();
+      }, 120);
+      return;
+    }
+
+    frameRef.current = window.requestAnimationFrame(step);
+  };
+
+  const start = () => {
+    if (isHolding) {
+      return;
+    }
+
+    clearFrame();
+    confirmedRef.current = false;
+    startRef.current = performance.now();
+    setHolding(true);
+    frameRef.current = window.requestAnimationFrame(step);
+  };
+
+  const cancel = () => {
+    if (!isHolding) {
+      return;
+    }
+
+    reset();
+  };
+
+  return {
+    progress,
+    isHolding,
+    start,
+    cancel,
+  };
+};

src/features/exit-hold/ui/ExitHoldButton.tsx

@@ -0,0 +1,119 @@
+'use client';
+
+import type { KeyboardEvent } from 'react';
+import { cn } from '@/shared/lib/cn';
+import { useHoldToConfirm } from '../model/useHoldToConfirm';
+
+interface ExitHoldButtonProps {
+  variant: 'bar' | 'ring';
+  onConfirm: () => void;
+  className?: string;
+}
+
+const RING_RADIUS = 13;
+const RING_CIRCUMFERENCE = 2 * Math.PI * RING_RADIUS;
+
+export const ExitHoldButton = ({
+  variant,
+  onConfirm,
+  className,
+}: ExitHoldButtonProps) => {
+  const { progress, isHolding, start, cancel } = useHoldToConfirm(onConfirm);
+  const ringOffset = RING_CIRCUMFERENCE * (1 - progress);
+
+  const handleKeyDown = (event: KeyboardEvent<HTMLButtonElement>) => {
+    if (event.key === ' ' || event.key === 'Enter') {
+      event.preventDefault();
+      start();
+    }
+  };
+
+  const handleKeyUp = (event: KeyboardEvent<HTMLButtonElement>) => {
+    if (event.key === ' ' || event.key === 'Enter') {
+      event.preventDefault();
+      cancel();
+    }
+  };
+
+  if (variant === 'ring') {
+    return (
+      <button
+        type="button"
+        aria-label="길게 눌러 나가기"
+        onMouseDown={start}
+        onMouseUp={cancel}
+        onMouseLeave={cancel}
+        onTouchStart={start}
+        onTouchEnd={cancel}
+        onTouchCancel={cancel}
+        onKeyDown={handleKeyDown}
+        onKeyUp={handleKeyUp}
+        onClick={(event) => event.preventDefault()}
+        className={cn(
+          'relative inline-flex h-9 w-9 items-center justify-center rounded-full bg-white/8 text-white/74 transition hover:bg-white/14 hover:text-white focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-sky-200/80',
+          isHolding && 'bg-white/16',
+          className,
+        )}
+      >
+        <svg
+          aria-hidden
+          className="-rotate-90 absolute inset-0 h-9 w-9"
+          viewBox="0 0 32 32"
+        >
+          <circle
+            cx="16"
+            cy="16"
+            r={RING_RADIUS}
+            fill="none"
+            stroke="rgba(255,255,255,0.2)"
+            strokeWidth="2"
+          />
+          <circle
+            cx="16"
+            cy="16"
+            r={RING_RADIUS}
+            fill="none"
+            stroke="rgba(186,230,253,0.92)"
+            strokeWidth="2"
+            strokeLinecap="round"
+            strokeDasharray={RING_CIRCUMFERENCE}
+            strokeDashoffset={ringOffset}
+          />
+        </svg>
+        <span aria-hidden className="relative z-10 text-[12px]">
+          ⤫
+        </span>
+      </button>
+    );
+  }
+
+  return (
+    <button
+      type="button"
+      aria-label="길게 눌러 나가기"
+      onMouseDown={start}
+      onMouseUp={cancel}
+      onMouseLeave={cancel}
+      onTouchStart={start}
+      onTouchEnd={cancel}
+      onTouchCancel={cancel}
+      onKeyDown={handleKeyDown}
+      onKeyUp={handleKeyUp}
+      onClick={(event) => event.preventDefault()}
+      className={cn(
+        'group relative overflow-hidden rounded-lg bg-white/8 px-2.5 py-1.5 text-xs text-white/82 transition hover:bg-white/14 hover:text-white focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-sky-200/80',
+        className,
+      )}
+    >
+      <span
+        aria-hidden
+        className="absolute inset-y-0 left-0 rounded-lg bg-sky-200/24 transition-[width] duration-75"
+        style={{ width: `${progress * 100}%` }}
+      />
+      <span className="relative z-10 inline-flex items-center gap-1">
+        <span aria-hidden>⤫</span>
+        <span>나가기</span>
+      </span>
+    </button>
+  );
+};