fix(10-13): escape modifier and capture-phase OS drop

- SearchBar.vue: add .prevent.stop to @keydown.escape to suppress browser native blur (Gap 5)
- OsDragOverlay.vue: register window drop listener with capture=true to fire before folder-row handlers (Gap 6)

frontend/src/components/documents/SearchBar.vue

@@ -8,7 +8,7 @@
       aria-label="Search documents"
       class="border border-gray-300 rounded-lg px-3 py-2 text-sm w-56 focus:outline-none focus:ring-2 focus:ring-indigo-500 focus:border-transparent"
       @input="emit('update:modelValue', $event.target.value)"
-      @keydown.escape="emit('update:modelValue', '')"
+      @keydown.escape.prevent.stop="emit('update:modelValue', '')"
     />
   </div>
 </template>

frontend/src/components/layout/OsDragOverlay.vue

@@ -53,13 +53,13 @@ export default {
     window.addEventListener('dragenter', this.onDragEnter)
     window.addEventListener('dragleave', this.onDragLeave)
     window.addEventListener('dragover', this.onDragOver)
-    window.addEventListener('drop', this.onDrop)
+    window.addEventListener('drop', this.onDrop, true)
   },
   beforeUnmount() {
     window.removeEventListener('dragenter', this.onDragEnter)
     window.removeEventListener('dragleave', this.onDragLeave)
     window.removeEventListener('dragover', this.onDragOver)
-    window.removeEventListener('drop', this.onDrop)
+    window.removeEventListener('drop', this.onDrop, true)
   },
 }
 </script>