[BUG] File upload system error state, users unable to upload further documents in new chats

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## 🐞Describe the bug

Having carried out multiple failed/errored conversations where multiple file uploads were attempted and API failures caused, the user is then unable to upload further files in a 'new chat'.

## 🔄 To Reproduce

Create a new chat, eg with Claude Haiku 4.5, upload 4-5 text files (in total under the 6MB limit), attempt to query with the files, inevitable failure message for whatever reason.

Repeat above frustratedly a few times, like a normal user would.

At some point of repeating the above, the user now attempts to upload just a single doc (less than 6MB) to a query, only to be told "The total file size must be no more than 6 MB.".

## 📷 Screenshots

## 🔎 Logs for Chat Issues

Have checked suggested logs and not found anything

## 📝 Additional context

Logging out doesn't remedy the error state, but waiting for some time seems to.

Document upload handling is generally unstable when subjected to realistic use cases, even within the 5 documents etc limit.

Seems to me like some background process re docs isn't being permitted to complete? Then isn't remedied/cancelled/documents queue cleared adequately when the user goes to create a new chat.

Using app as deployed by Codebuild/Cloud shell

No files, tests, or entry points are named. Reproduce the upload failure sequence across several new chats, then trace the document-upload state and its reset or cleanup between chats; done means a failed upload does not prevent a later valid upload under the 6 MB limit.

Written by the indexing model from the issue text.