workspace.openFolder (default mod+o, the editor-standard open-folder chord)
runs openFolderAsProject: pick a folder, enter the project that already owns
it or create one named after the folder, scope the sidebar, and land on a
fresh session draft anchored there. A stale backend without the projects.*
RPC still gets the workspace session, with a warning.
StartWorkSessionRequest grows an openTab flag so these opens-from-nowhere
stack a tab instead of spending an occupied main, and goToProject/
resolveNewSessionCwd share one projectRootCwd resolver.
5affcd6bf4