Soul's mutation pass on 375d6bd4 found 8 of 9 validator mutations
surviving, including the `..` model-path guard and the prefab refusal. The
validator had five hand-picked cases. ShipValidationTests now carries one
case per guard: each starts from the valid fixture, breaks exactly one
thing, and names the message that guard alone produces. It also pins the ID
alphabet at both ends of each range, the accepted model-asset spellings
beside the refused ones, the range edges of point attributes, an anchor
naming its hardpoint as parent, and Read's exactly-one-record and
validate-on-load behaviour.
ShipAuthoringTests.Fixture becomes internal so the new file shares it.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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