Canonical location of the published JSON Schema for .robin.json. Generated
configs point their $schema here so editors can offer autocomplete and
validation.
Walks up from start (inclusive) looking for the first directory that
contains a .robin.json. Returns the path to that config, or None when no
ancestor holds one. This lets robin be run from any subdirectory of a
project, mirroring how git and cargo locate their root files.
Resolves the config path for read commands: the nearest .robin.json found
by walking up from the current directory, falling back to ./.robin.json
so that “not found” errors still name a sensible location.