How can I upload or attach files into the Amazon Q chat dialogue for VS Code?

## System details (run `AWS: About` and/or `Amazon Q: About`)
OS: Windows_NT x64 10.0.22631
Visual Studio Code extension host: 1.93.1
Amazon Q: 1.25.0
node: 20.15.1
electron: 30.4.0

## Question
How do I upload or attach files into the Amazon Q chat dialogue?
Q tells me that "If you need me to provide an analysis of the complete project structure, dependencies, or any other files, you would need to share that information by uploading, attaching, or pasting the relevant file contents or directory listings directly into our conversation.", however I can find no way to do so.
The chat input appears to allow dropping of files into it, but nothing appears to happen when I attempt to do so.
I've attempted to use the "@workspace" directive as described at https://docs.aws.amazon.com/amazonq/latest/qdeveloper-ug/workspace-context.html, but it also does not seem to work.

Read the linked Amazon Q workspace-context documentation and reproduce the reported drag-and-drop and @workspace behavior in the VS Code extension using the stated versions. Done means documenting whether file attachment is supported and providing verified steps or clarifying the limitation.

Written by the indexing model from the issue text.