feat(space/hud): Exit 버튼 좌측 하단 Invisible Door UI로 재배치

맥락:
- 기존의 우측 상단 Exit(나가기) 버튼이 너무 동떨어져 있었음.
- 목표(Goal) 패널 하단에 Exit 버튼을 두려는 시도가 있었으나, '목표 유지'와 '목표 포기(Exit)'라는 상반된 의미가 한 공간에 묶여 인지적 충돌을 발생시킴.
- 몰입을 방해하지 않는 투명함(Invisible UI)과 본능적인 이탈 경로가 필요함.

변경사항:
- SpaceToolsDockWidget에 새로운 좌측 하단(Bottom-Left) 모서리 Exit 버튼 렌더링 영역 추가.
- 평소에는 투명한 Escape(⎋) 아이콘만 노출하여 배경 공간의 방해 최소화.
- 사용자가 마우스를 Hover할 때만 알약(Pill) 형태로 부드럽게 확장(Expansion)되며 ExitHoldButton(Bar)이 나타나는 고급 인터랙션 구현.
- FloatingGoalWidget에 테스트로 추가했던 Exit 버튼 코드 원복(제거) 및 SpaceFocusHudWidget, SpaceWorkspaceWidget의 불필요한 prop 전달 정리.

검증:
- npm run build 정상 통과.

세션-상태: 몰입 공간(/space)의 하이엔드 UI 레이아웃 재배치 및 디자인 고도화 완료.
세션-다음: 향후 필요 시 통계(Analytics) 또는 결제(Paywall) 세부 기능 구현.
세션-리스크: 없음.

src/widgets/space-focus-hud/ui/FloatingGoalWidget.tsx

@@ -23,10 +23,10 @@ export const FloatingGoalWidget = ({
   const normalizedGoal = goal.trim().length > 0 ? goal.trim() : copy.space.timerHud.goalFallback;
 
   return (
-    <div className="pointer-events-none fixed left-0 top-0 z-20 w-full max-w-[800px] h-48 bg-[radial-gradient(ellipse_at_top_left,rgba(0,0,0,0.6)_0%,rgba(0,0,0,0)_60%)]">
+    <div className="pointer-events-none fixed left-0 top-0 z-20 w-full max-w-[800px] h-48 bg-[radial-gradient(ellipse_at_top_left,rgba(0,0,0,0.6)_0%,rgba(0,0,0,0)_60%)] group">
       <div className="flex flex-col items-start gap-4 p-8 md:p-12">
         {/* Main Goal */}
-        <div className="pointer-events-auto group relative flex items-center gap-4">
+        <div className="pointer-events-auto flex items-center gap-4">
           <h2 className="text-2xl md:text-[1.75rem] font-medium tracking-tight text-white drop-shadow-[0_2px_4px_rgba(0,0,0,0.8)] [text-shadow:0_4px_24px_rgba(0,0,0,0.6)]">
             {normalizedGoal}
           </h2>
@@ -34,7 +34,7 @@ export const FloatingGoalWidget = ({
             <button
               type="button"
               onClick={onGoalCompleteRequest}
-              className="opacity-0 group-hover:opacity-100 shrink-0 rounded-full border border-white/20 bg-black/40 backdrop-blur-md px-3.5 py-1.5 text-[11px] font-medium text-white/90 shadow-lg transition-all hover:bg-black/60 hover:text-white"
+              className="opacity-0 group-hover:opacity-100 shrink-0 rounded-full border border-white/20 bg-black/40 backdrop-blur-md px-3.5 py-1.5 text-[11px] font-medium text-white/90 shadow-lg transition-all hover:bg-black/60 hover:text-white focus-visible:opacity-100"
             >
               목표 달성
             </button>

src/widgets/space-focus-hud/ui/SpaceFocusHudWidget.tsx

@@ -21,6 +21,7 @@ interface SpaceFocusHudWidgetProps {
   onStartRequested?: () => void;
   onPauseRequested?: () => void;
   onRestartRequested?: () => void;
+  onExitRequested?: () => void;
   onGoalUpdate: (nextGoal: string) => boolean | Promise<boolean>;
   onStatusMessage: (payload: HudStatusLinePayload) => void;
 }
@@ -41,6 +42,7 @@ export const SpaceFocusHudWidget = ({
   onStartRequested,
   onPauseRequested,
   onRestartRequested,
+  onExitRequested,
   onGoalUpdate,
   onStatusMessage,
 }: SpaceFocusHudWidgetProps) => {

src/widgets/space-tools-dock/ui/SpaceToolsDockWidget.tsx

@@ -155,15 +155,23 @@ export const SpaceToolsDockWidget = ({
     <>
       <div
         className={cn(
-          'fixed z-30 transition-opacity right-[calc(env(safe-area-inset-right,0px)+0.75rem)] top-[calc(env(safe-area-inset-top,0px)+0.75rem)]',
-          isFocusMode ? (isIdle ? 'opacity-40' : 'opacity-84') : 'opacity-92',
+          'fixed z-30 transition-all duration-300 left-[calc(env(safe-area-inset-left,0px)+2rem)] bottom-[calc(env(safe-area-inset-bottom,0px)+2rem)] group flex items-center justify-start',
+          isFocusMode ? (isIdle ? 'opacity-0 -translate-x-4 pointer-events-none' : 'opacity-80 hover:opacity-100') : 'opacity-92',
         )}
       >
+        <div className="relative flex items-center justify-start overflow-hidden rounded-full border border-white/10 bg-black/20 p-1.5 backdrop-blur-md transition-all duration-300 ease-out w-10 hover:w-[130px] hover:bg-black/40">
+          <div className="flex shrink-0 h-7 w-7 items-center justify-center text-white/70">
+            <span aria-hidden className="text-[14px]">⎋</span>
+          </div>
+          <div className="absolute left-10 whitespace-nowrap opacity-0 transition-opacity duration-300 group-hover:opacity-100">
             <ExitHoldButton
-          variant={isFocusMode ? 'ring' : 'bar'}
+              variant="bar"
               onConfirm={onExitRequested}
+              className="bg-transparent text-white/90 hover:bg-white/10 hover:text-white px-2 py-1 h-7"
             />
           </div>
+        </div>
+      </div>
 
       <FocusModeAnchors
         isFocusMode={isFocusMode}

src/widgets/space-workspace/ui/SpaceWorkspaceWidget.tsx

@@ -291,7 +291,7 @@ export const SpaceWorkspaceWidget = () => {
         visible={isFocusMode}
         hasActiveSession={Boolean(currentSession)}
         playbackState={resolvedPlaybackState}
-        sessionPhase={phase ?? "focus"}
+        sessionPhase={phase ?? 'focus'}
         isSessionActionPending={isSessionMutating}
         canStartSession={controls.canStartSession}
         canPauseSession={controls.canPauseSession}
@@ -305,6 +305,9 @@ export const SpaceWorkspaceWidget = () => {
         onRestartRequested={() => {
           void controls.handleRestartRequested();
         }}
+        onExitRequested={() => {
+          void controls.handleExitRequested();
+        }}
         onStatusMessage={pushStatusLine}
         onGoalUpdate={controls.handleGoalAdvance}
       />