## Why
`ApiPathString` kind of implies that it can be used anywhere we pull a
path out of JSON, but it's not really appropriate for tool arguments
when the model might generate relative paths.
Prefer `String` for model-generated paths and we can handle the
conversion per feature for now and define a shared abstraction later if
it makes sense.
# What
Rename `ApiPathString` to `AppLegacyPathString` to clarify its role.
Expand the `path-types` skill to tell the model to leave tool args as
bare strings.