Feature: Mobile bottom-sheet drawer (slide-up from bottom, swipe-down to close, overlay), update AGENTS.md to v4.0

src/app/globals.css

@@ -1553,20 +1553,39 @@ a { color: inherit; text-decoration: none; }
     box-shadow: var(--shadow-lg);
   }
 
+  /* 모바일: 우측 패널을 바닥에서 위로 슬라이드 업하는 바텀 시트 */
   .detail-panel {
     position: fixed;
+    left: 0;
     right: 0;
-    top: 0;
     bottom: 0;
-    z-index: 30;
-    transform: translateX(100%);
-    transition: transform var(--dur-slow) var(--ease-out);
+    top: auto;
+    height: 92dvh;      /* 전체 화면의 92% */
     width: 100% !important;
+    border-left: none;
+    border-top: 1px solid var(--border);
+    border-radius: var(--radius-lg) var(--radius-lg) 0 0;
+    z-index: 35;
+    transform: translateY(100%);
+    transition: transform var(--dur-slow) var(--ease-out);
+    box-shadow: 0 -8px 40px rgba(0, 0, 0, 0.18);
+    overflow: hidden;
   }
 
   .detail-panel.mobile-open {
-    transform: translateX(0);
-    box-shadow: var(--shadow-panel);
+    transform: translateY(0);
+  }
+
+  /* 모바일 학 스와이프 핸들 */
+  .mobile-swipe-handle {
+    display: block !important;
+    width: 40px;
+    height: 5px;
+    background: var(--border-medium);
+    border-radius: var(--radius-full);
+    margin: 8px auto 4px;
+    cursor: grab;
+    flex-shrink: 0;
   }
 
   .bottom-nav {
@@ -1579,6 +1598,20 @@ a { color: inherit; text-decoration: none; }
 
   .task-item { padding: 10px 16px; }
   .main-header { padding: 0 16px; }
+
+  .mobile-only {
+    display: block;
+  }
+
+  /* 바텀시트 배경 오버레이 */
+  .bottom-sheet-overlay {
+    display: block;
+    position: fixed;
+    inset: 0;
+    background: rgba(0, 0, 0, 0.45);
+    z-index: 34;
+    animation: fadeIn var(--dur-normal) var(--ease-out);
+  }
 }
 
 /* Bottom nav (mobile only) */
@@ -1680,6 +1713,11 @@ a { color: inherit; text-decoration: none; }
   display: none;
 }
 
+/* 바텀시트 배경 오버레이 (모바일 전용) */
+.bottom-sheet-overlay {
+  display: none;
+}
+
 /* ============================================
    CUSTOM CONTEXT MENU
    ============================================ */