Clicking on a file in AI context does not open file

[colin-grant-work]

Bug Description:

It appears that there was a recent change to resolve context files to a fake absolute path with a prefix /home/user/workspaces. That seems to have broken the functionality that allowed files in context to be opened on click.

Steps to Reproduce:

1. Add a file to the AI context.
2. Close it if it's currently open.
3. Click on that file's context item.
4. Observe that the editor is not opened, and an error is logged:

Additional Information

• Operating System: MacOS
• Theia Version: f6c36e1 (1.65 dev)