The OSS access-control form currently lets a plugin replace the
`allowed_users` policy entry. Multi-tenancy also wants:
- an extra radio option for "Org-scoped" sitting in front of the
built-ins, and
- a context-sensitive create-time default (routes inside a non-
platform Org should land on the Org-scoped policy rather than
`authed`).
Extend the `accessControl` slot with two more hooks:
- `prependedPolicies?: { policyValue, labelId, tipsId?, Field? }[]`
— entries prepended to the radio group; each may carry an
optional content `Field` rendered when selected.
- `resolveCreateDefault?: () => string | undefined` — overrides the
initial `access_policy` for the create flow; the OSS fallback is
still `authed`.
The host's tooltip list mirrors the same order. Existing behaviour
without a plugin is unchanged.
