Owned files, adopt and unbind

The ownership baseline records every file Workloom wrote for a workspace, and Workloom rewrites or removes only those owned files. If a file already existed where a package wants to write, `--adopt` backs it up first and then takes ownership.

`wl restore` rewrites owned files back to their render-plan content. `wl unbind` undoes a workspace on this machine: adopted originals come back from backup, owned files are removed and local state is cleared.