Add touch drag-to-dismiss gesture to BottomSheet

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

frontend/src/components/BottomSheet.vue

@@ -2,7 +2,18 @@
   <Teleport to="body">
     <Transition name="sheet">
       <div v-if="open" class="sheet-backdrop" @click.self="$emit('close')" @keydown.escape="$emit('close')">
-        <div class="sheet" role="dialog" aria-modal="true" :aria-label="label" ref="sheetEl" tabindex="-1">
+        <div
+          class="sheet"
+          role="dialog"
+          aria-modal="true"
+          :aria-label="label"
+          ref="sheetEl"
+          tabindex="-1"
+          :style="dragStyle"
+          @touchstart="onTouchStart"
+          @touchmove="onTouchMove"
+          @touchend="onTouchEnd"
+        >
           <div class="sheet__handle" aria-hidden="true" />
           <slot />
         </div>
@@ -12,14 +23,14 @@
 </template>
 
 <script setup lang="ts">
-import { ref, watch, nextTick } from 'vue'
+import { ref, computed, watch, nextTick } from 'vue'
 
 defineProps<{
   open: boolean
   label: string
 }>()
 
-defineEmits<{
+const emit = defineEmits<{
   close: []
 }>()
 
@@ -39,6 +50,45 @@ watch(
     }
   },
 )
+
+/* ── Drag-to-dismiss ── */
+const DISMISS_THRESHOLD = 100
+const dragY = ref(0)
+const dragging = ref(false)
+let startY = 0
+
+const dragStyle = computed(() => {
+  if (!dragging.value || dragY.value <= 0) return undefined
+  return {
+    transform: `translateY(${dragY.value}px)`,
+    transition: 'none',
+  }
+})
+
+function onTouchStart(e: TouchEvent) {
+  const touch = e.touches[0]
+  if (!touch) return
+  startY = touch.clientY
+  dragging.value = true
+  dragY.value = 0
+}
+
+function onTouchMove(e: TouchEvent) {
+  if (!dragging.value) return
+  const touch = e.touches[0]
+  if (!touch) return
+  const delta = touch.clientY - startY
+  if (delta > 0) e.preventDefault()
+  dragY.value = Math.max(0, delta)
+}
+
+function onTouchEnd() {
+  if (dragY.value >= DISMISS_THRESHOLD) {
+    emit('close')
+  }
+  dragging.value = false
+  dragY.value = 0
+}
 </script>
 
 <style scoped>