ControlBy, Model, ModelTime, ActiveRecord, BaseUser, Response, Page,
Migration and the menu type constants now read `type X = pkg.X` /
`const X = pkg.X` against go-admin-core's sdk/contract/models instead
of defining these shapes locally. Every embed, GORM tag and JSON tag
is unchanged - a type alias is the same type, not a new one - and
every existing import of go-admin/common/models keeps compiling with
no changes of its own (verified with `git diff --exit-code` over the
70 files that import common/models, common/dto or common/actions).
The menu type constants (Directory/Menu/Button) are declared as direct
references rather than restated literals: an independently written
copy of the same value can be edited out of step with go-admin-core's,
where a direct reference cannot (PRD 006 hard constraint 4).
PRD 006 F1/F5.
Claude-Session: https://claude.ai/code/session_01HPTAw8b8tAdFNFn8rKdPYx
zhangwenjian