fix(ui): capture active folder for storage upload target

Upload was always going to root because activeFolder derived from
activePath which only tracks file selections (folders expand instead
of selecting). Now capture the folder at Upload button click time
and show the target path in the dialog description.

ui/web/src/pages/storage/storage-page.tsx

@@ -125,23 +125,23 @@ export function StoragePage() {
     refreshSize();
   }, [listFiles, refreshSize]);
 
-  /** Derive current folder path from activePath for scoped uploads. */
+  /** Derive the folder containing the currently selected file (or "" for root). */
   const activeFolder = useMemo(() => {
     if (!activePath) return "";
-    // If activePath is a folder, use it; otherwise use its parent.
-    const node = files.find((f) => f.path === activePath);
-    if (node?.isDir) return activePath;
     const idx = activePath.lastIndexOf("/");
     return idx > 0 ? activePath.slice(0, idx) : "";
-  }, [activePath, files]);
+  }, [activePath]);
+
+  // uploadFolder is captured when user clicks Upload, so it won't change mid-dialog.
+  const [uploadFolder, setUploadFolder] = useState("");
 
   const handleUploadFile = useCallback(async (file: File) => {
     const params: Record<string, string> = {};
-    if (activeFolder) params["path"] = activeFolder;
+    if (uploadFolder) params["path"] = uploadFolder;
     const fd = new FormData();
     fd.append("file", file);
     await http.upload(`/v1/storage/files?` + new URLSearchParams(params).toString(), fd);
-  }, [http, activeFolder]);
+  }, [http, uploadFolder]);
 
   const handleUploadClose = useCallback((v: boolean) => {
     setUploadOpen(v);
@@ -178,7 +178,7 @@ export function StoragePage() {
         }
         actions={
           <div className="flex items-center gap-2">
-            <Button variant="outline" size="sm" onClick={() => setUploadOpen(true)}>
+            <Button variant="outline" size="sm" onClick={() => { setUploadFolder(activeFolder); setUploadOpen(true); }}>
               <Upload className="h-4 w-4 mr-1.5" />
               {t("common:uploadLabel", "Upload")}
             </Button>
@@ -211,7 +211,7 @@ export function StoragePage() {
         onOpenChange={handleUploadClose}
         onUpload={handleUploadFile}
         title={t("upload.title")}
-        description={t("upload.description")}
+        description={uploadFolder ? `${t("upload.description")} → ${uploadFolder}/` : t("upload.description")}
       />
 
       {/* Delete confirmation dialog */}