fix(demo-data): attribute the descriptor to the app id, not the directory

`x-openregister.app` is what the descriptor inventory resolves a register to
an app by, and the generator was writing the CHECKOUT DIRECTORY name into it —
naming an app that does not exist. A cross-app id is a runtime lookup: it
finds nobody rather than erroring. The file is renamed to match and the
directory-named one removed, so exactly one mock descriptor remains.

Author: Conduction Release Bot