match_members tried the slugified handle before display names, so a Desktop
snapshot member "Herring" bound to an unrelated CLI persona at d-tag
`herring` even when the UUID persona with that display name existed — a
silent wrong roster, and the ambiguous-name error never ran. Order is now
exact d-tag, unique display name (ambiguity errors), then slugified d-tag.
The slug fall-through keeps resolving handles that are prettied forms of a
CLI slug with a different display name.
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