fix(core): harden download lifecycle and scheduling

src/utils/downloadActions.ts

@@ -2,6 +2,7 @@ import type { DownloadStatus } from '../bindings/DownloadStatus';
 
 const STARTABLE_STATUSES: ReadonlySet<DownloadStatus> = new Set([
   'ready',
+  'staged',
   'paused',
   'failed',
 ]);
@@ -29,7 +30,7 @@ export const canRedownload = (status: DownloadStatus): boolean =>
   REDOWNLOADABLE_STATUSES.has(status);
 
 export const startActionLabel = (status: DownloadStatus): 'Start' | 'Resume' =>
-  status === 'ready' || status === 'failed' ? 'Start' : 'Resume';
+  status === 'ready' || status === 'staged' || status === 'failed' ? 'Start' : 'Resume';
 
 export const isTransferLocked = (status: DownloadStatus): boolean =>
   status === 'downloading' || status === 'processing' || status === 'retrying';

src/utils/downloads.ts

@@ -83,6 +83,15 @@ export const fileNameFromUrl = (rawUrl: string): string => {
   return 'download';
 };
 
+export const canonicalizeDownloadFileName = (fileName: string): string => {
+  const leaf = fileName.replace(/\\/g, '/').split('/').pop() || 'download';
+  const sanitized = leaf
+    .replace(/[\u0000-\u001f<>:"/\\|?*]/g, '-')
+    .trim()
+    .replace(/[. ]+$/g, '');
+  return sanitized && sanitized !== '.' && sanitized !== '..' ? sanitized : 'download';
+};
+
 export const isMediaUrl = (rawUrl: string): boolean => {
   try {
     const url = new URL(rawUrl);