VS Code extension adds drive root (c:\) as working directory for a non-file workspace folder

Environment

• Claude Code CLI 2.1.286 / 2.1.287, VS Code extension 2.1.285, Windows
• Workspace containing a folder from a virtual file system extension (custom URI scheme, e.g. adt://system/ from the "ABAP remote filesystem" extension)

Description
For a multi-root workspace with a local folder and a folder with a non-file URI scheme, the panel turns the non-file folder into c:\ and passes it as an additional working directory. The session can then read the whole drive without prompts.

Steps to reproduce

1. Workspace file with two folders: "path": "agent" (local) and a folder with uri "adt://system/" provided by a file system extension.
2. Open the workspace, Claude Code panel, new session, /permissions.

Actual

• Local folder first: working folder c:\dev\agent, and c:\ listed under Workspace "From startup options". Read without prompt anywhere on C:.
• Virtual folder first: working folder C:\ ("Original working directory"), only user settings are loaded, Allow/Ask/Deny 0 - project permissions are not applied at all.
• Terminal (claude in C:\dev\agent): Workspace only C:\dev\agent.

Expected
Folders with a non-file URI scheme are not passed as working directories, or are passed under their own scheme - never as the drive root.

Impact
Project deny rules are the only protection against reading other projects' credentials and session transcripts; with c:\ in scope this depends on how complete the deny list is.