`subsume` RelationshipType has no inverse

### Version of Gemara

`v1.5.0`

### Describe the bug

`RelationshipType` has eight members:
`implements`, `implemented_by`, `supports`, `supported_by`, `equivalent`, `subsumes`, `relates_to`, `no_match`. `implements`/`implemented-by` and `supports`/`supported-by` are directional pairs; `equivalent` and `relates-to` are symmetric and need no inverse; `subsumes` (`⊃`, "source contains target") is asymmetric and has no partner.

### To Reproduce

Visit https://github.com/gemaraproj/gemara/blob/24e52e93bc71e28507e1942ce543e26ab58a7f25/mappingdocument.cue#L91

### Expected behavior

`subsume` to have an inverse for consistency with the other relationship types

### Screenshots

_No response_

### Additional context

_No response_

Open mappingdocument.cue around line 91 and inspect the RelationshipType members and their directional pairings. Define the missing inverse for subsumes consistently with the existing relationship types, then confirm the RelationshipType definition contains the expected inverse.

Written by the indexing model from the issue text.