refactor(focus): 몰입모드 토글 제거 및 Focus-First 기본 구조로 전환

맥락:
- 몰입모드 토글은 상태 인지 비용을 높여 집중 흐름을 끊고, Quick Controls 헤더를 대시보드형으로 보이게 만들고 있었습니다.

변경사항:
- Quick Controls에서 기본/몰입 모드 토글 UI를 완전히 제거했습니다.
- Focus 화면의 HUD 톤은 외부 모드 상태 없이 항상 몰입 톤으로 렌더링되도록 고정했습니다.
- workspace/tools-dock/focus-hud 간 모드 토글 상태 전달 경로를 정리해, 컨트롤은 패널을 열었을 때만 보이는 Focus-First 흐름으로 단순화했습니다.

검증:
- npx tsc --noEmit

세션-상태: 모드 토글 없이 패널 열림 상태만으로 컨트롤 노출이 정의됩니다.
세션-다음: (선택) 컨트롤 자동 숨김 표시 정책 옵션을 패널 내부에 추가합니다.
세션-리스크: 자동 숨김 정책이 아직 없어 패널을 열어둔 채 방치되는 경우 수동 닫기가 필요합니다.

src/widgets/control-center-sheet/ui/ControlCenterSheetWidget.tsx

@@ -16,11 +16,9 @@ interface ControlCenterSheetWidgetProps {
   rooms: RoomTheme[];
   selectedRoomId: string;
   selectedTimerLabel: string;
-  isImmersionMode: boolean;
   sceneRecommendedSoundLabel: string;
   sceneRecommendedTimerLabel: string;
   timerPresets: TimerPreset[];
-  onImmersionModeChange: (next: boolean) => void;
   onSelectRoom: (roomId: string) => void;
   onSelectTimer: (timerLabel: string) => void;
   onLockedClick: (source: string) => void;
@@ -49,11 +47,9 @@ export const ControlCenterSheetWidget = ({
   rooms,
   selectedRoomId,
   selectedTimerLabel,
-  isImmersionMode,
   sceneRecommendedSoundLabel,
   sceneRecommendedTimerLabel,
   timerPresets,
-  onImmersionModeChange,
   onSelectRoom,
   onSelectTimer,
   onLockedClick,
@@ -74,41 +70,6 @@ export const ControlCenterSheetWidget = ({
 
   return (
     <div className="space-y-4">
-      <section className="space-y-2 rounded-2xl border border-white/12 bg-black/22 p-3 backdrop-blur-md">
-        <div className="flex items-center justify-between gap-2">
-          <p className="text-[11px] text-white/64">모드</p>
-          <div className="inline-flex items-center rounded-full border border-white/14 bg-white/[0.03] p-0.5">
-            <button
-              type="button"
-              onClick={() => onImmersionModeChange(false)}
-              className={cn(
-                'h-7 rounded-full border px-3 text-[11px] transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-sky-200/70',
-                !isImmersionMode
-                  ? 'border-white/15 bg-white/10 text-white/90'
-                  : 'border-white/10 bg-transparent text-white/60 hover:text-white/78',
-              )}
-            >
-              기본
-            </button>
-            <button
-              type="button"
-              onClick={() => onImmersionModeChange(true)}
-              className={cn(
-                'h-7 rounded-full border px-3 text-[11px] transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-sky-200/70',
-                isImmersionMode
-                  ? 'border-white/15 bg-white/10 text-white/90'
-                  : 'border-white/10 bg-transparent text-white/60 hover:text-white/78',
-              )}
-            >
-              몰입
-            </button>
-          </div>
-        </div>
-        <p className="text-[11px] text-white/54">
-          {isImmersionMode ? '필수만 남기고 숨김' : '모든 컨트롤 표시'}
-        </p>
-      </section>
-
       <section className="space-y-2.5 rounded-2xl border border-white/12 bg-black/22 p-3.5 backdrop-blur-md">
         <SectionTitle title="Scene" description={selectedRoom?.name ?? '공간'} />
         <div

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

@@ -9,7 +9,6 @@ interface SpaceFocusHudWidgetProps {
   goal: string;
   timerLabel: string;
   visible: boolean;
-  isImmersionMode: boolean;
   onGoalUpdate: (nextGoal: string) => void;
   statusLine: HudStatusLineItem | null;
   onStatusAction: () => void;
@@ -20,7 +19,6 @@ export const SpaceFocusHudWidget = ({
   goal,
   timerLabel,
   visible,
-  isImmersionMode,
   onGoalUpdate,
   statusLine,
   onStatusAction,
@@ -110,7 +108,7 @@ export const SpaceFocusHudWidget = ({
               }
             : null
         }
-        isImmersionMode={isImmersionMode}
+        isImmersionMode
         className="pr-[4.2rem]"
         onGoalCompleteRequest={handleOpenCompleteSheet}
         onStatusAction={onStatusAction}

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

@@ -20,7 +20,6 @@ import { QuickSoundPopover } from './popovers/QuickSoundPopover';
 import { InboxToolPanel } from './panels/InboxToolPanel';
 interface SpaceToolsDockWidgetProps {
   isFocusMode: boolean;
-  isImmersionMode: boolean;
   rooms: RoomTheme[];
   selectedRoomId: string;
   selectedTimerLabel: string;
@@ -43,14 +42,12 @@ interface SpaceToolsDockWidgetProps {
   onRestoreThought: (thought: RecentThought) => void;
   onClearInbox: () => RecentThought[];
   onResetToSceneRecommended: () => void;
-  onImmersionModeChange: (next: boolean) => void;
   onStatusMessage: (payload: HudStatusLinePayload) => void;
   onExitRequested: () => void;
 }
 
 export const SpaceToolsDockWidget = ({
   isFocusMode,
-  isImmersionMode,
   rooms,
   selectedRoomId,
   selectedTimerLabel,
@@ -73,7 +70,6 @@ export const SpaceToolsDockWidget = ({
   onRestoreThought,
   onClearInbox,
   onResetToSceneRecommended,
-  onImmersionModeChange,
   onStatusMessage,
   onExitRequested,
 }: SpaceToolsDockWidgetProps) => {
@@ -415,11 +411,9 @@ export const SpaceToolsDockWidget = ({
             rooms={rooms}
             selectedRoomId={selectedRoomId}
             selectedTimerLabel={selectedTimerLabel}
-            isImmersionMode={isImmersionMode}
             sceneRecommendedSoundLabel={sceneRecommendedSoundLabel}
             sceneRecommendedTimerLabel={sceneRecommendedTimerLabel}
             timerPresets={timerPresets}
-            onImmersionModeChange={onImmersionModeChange}
             onSelectRoom={(roomId) => {
               onRoomSelect(roomId);
             }}

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

@@ -167,7 +167,6 @@ export const SpaceWorkspaceWidget = () => {
   );
 
   const [workspaceMode, setWorkspaceMode] = useState<WorkspaceMode>('setup');
-  const [isImmersionMode, setImmersionMode] = useState(false);
   const [selectedRoomId, setSelectedRoomId] = useState(initialRoomId);
   const [selectedTimerLabel, setSelectedTimerLabel] = useState(initialTimerLabel);
   const [goalInput, setGoalInput] = useState(initialGoal);
@@ -378,7 +377,6 @@ export const SpaceWorkspaceWidget = () => {
         goal={goalInput.trim()}
         timerLabel={selectedTimerLabel}
         visible={isFocusMode}
-        isImmersionMode={isImmersionMode}
         statusLine={activeStatus}
         onStatusAction={runActiveAction}
         onStatusMessage={pushStatusLine}
@@ -407,8 +405,6 @@ export const SpaceWorkspaceWidget = () => {
         onSetSoundVolume={setMasterVolume}
         isSoundMuted={isMuted}
         onSetSoundMuted={setMuted}
-        isImmersionMode={isImmersionMode}
-        onImmersionModeChange={setImmersionMode}
         onCaptureThought={(note) => addThought(note, selectedRoom.name)}
         onDeleteThought={removeThought}
         onSetThoughtCompleted={setThoughtCompleted}