fix: update workspace item drag cursor

[astyfx]

Summary

• Change project and workspace sidebar rows to show the normal pointer cursor on hover.
• Keep the grabbing cursor only while pressing or actively dragging sortable rows.

Root Cause

The sortable row activator applied cursor-grab to the whole clickable row, so hovering over workspace items always looked like a drag affordance even before press-and-hold drag activation.

Verification

• bunx --bun prettier --write src/components/layout/ProjectWorkspaceSidebar.tsx
• bun run typecheck