Remote Control app: file delivery via SendUserFile fails silently (red error triangle), tool reports success

When a Claude Code session sends a file to the user via the SendUserFile mechanism while the user is on the Remote Control mobile app, the file fails to open — shown as a red warning triangle on the file card — even though the tool call itself reports a successful send. This is reproducible (hit twice, ~1 month apart) and affects any file type. Workaround found: sending the same file via email attachment instead works reliably. Would appreciate this being looked at, since it silently breaks a documented capability (SendUserFile) specifically on the mobile Remote Control surface.

Start by reproducing the documented SendUserFile flow from a Claude Code session to the Remote Control mobile app, checking the file card and tool result. Compare it with the working email-attachment workaround; done means files of different types open successfully in the mobile app and failures are no longer reported as successful sends.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.