[BUG] Cowork on Windows cannot write files to virtual network drives (e.g. Z: mapped to Zoho WorkDrive)

Describe the bug
Cowork on Windows allows users to add a virtual network drive as a working folder (e.g. a Z: drive mapped to Zoho WorkDrive via its desktop sync client). However, any attempt by Cowork to write files to that drive fails. The folder appears to mount and be accepted by the folder picker, but writes do not complete successfully.

To reproduce

1. Install Zoho WorkDrive desktop sync client on Windows — this maps a virtual network drive (e.g. Z:).
2. Open Cowork and select a folder on the Z: drive as the working directory.
3. Ask Claude to create or write a file in that directory.
4. Observe that the write fails.

Expected behaviour
Files should be written successfully to the selected folder on the virtual network drive, consistent with behaviour on local NTFS drives.

Actual behaviour
File write fails. The virtual network drive is accepted by the folder picker, but writes do not succeed.

Environment

• OS: Windows
• Product: Claude Desktop — Cowork mode (Research Preview)
• Drive type: Virtual network drive mapped to Zoho WorkDrive (Z:)

Additional context
This is distinct from existing issues #29583 and #33590 (which are about the folder picker rejecting non-home paths): here the folder IS accepted by the picker, but writing fails. May be related to #25293 (OneDrive virtiofs issues) and #27594 (VirtioFS I/O errors), as the underlying mechanism — virtiofs/Plan9 host-share protocol encountering a virtual filesystem driver — is likely similar. Other virtual drive setups (e.g. Google Drive for Desktop, OneDrive in local-sync mode) may be affected similarly.