feat(grant): name org members, from a refreshed core spec

The vendored core spec was last refreshed on 2026-09-23, and core has since added displayName to org members. Refresh it and regenerate.

org grant list gains a NAME column and the org pickers label each member handle · name, so a Google account (whose handle is only a subject id) reads as a person. Rows without a name show "-"; --json carries displayName as sent. Project and repo grants don't carry a name on the wire yet; core is adding it.

The refresh also changes two shapes the CLI reads:

• GetRepo now returns RepoHeaders (body under Response, plus Retry-After), so the three GetRepo interfaces and their callers read .Response.
• Org members decode as OrgMemberListItem, whose role/status are now enums. They join Membership in normalize.go's loosened read-model enums, so a status the CLI doesn't know (e.g. "invited") still decodes instead of failing the whole listing.