File browser: upload progress bar (0.21.5)

filesApi.upload now accepts an onProgress callback wired to axios
onUploadProgress; the Files page shows a progress bar with percentage
while uploading. Single-file upload tracks that file's bytes; folder
upload tracks overall progress across the N files (file i/N + current
file's bytes).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/api/files.ts

@@ -63,13 +63,27 @@ export const filesApi = {
     triggerDownload(res.data as Blob, filename);
   },
 
-  upload: async (path: string, file: File, overwrite = false, relPath = "", agentId?: number) => {
+  upload: async (
+    path: string,
+    file: File,
+    overwrite = false,
+    relPath = "",
+    agentId?: number,
+    onProgress?: (pct: number) => void,
+  ) => {
     const form = new FormData();
     form.append("path", path);
     form.append("overwrite", String(overwrite));
     if (relPath) form.append("rel_path", relPath);
     form.append("file", file);
-    const res = await api.post<{ ok: boolean; name: string }>(`${base(agentId)}/upload`, form);
+    const res = await api.post<{ ok: boolean; name: string }>(`${base(agentId)}/upload`, form, {
+      onUploadProgress: onProgress
+        ? (e) => {
+            const pct = e.total ? (e.loaded / e.total) * 100 : (e.progress ?? 0) * 100;
+            onProgress(Math.min(pct, 100));
+          }
+        : undefined,
+    });
     return res.data;
   },
 };