`?preview_draft=<sid>` on any page/post route forwards the signed
session id to the CMS, which renders the in-memory draft instead of
the persisted entry. Layout listens for `rustycms:reload` postMessages
from the admin iframe parent and re-runs `invalidateAll()` to pick up
fresh draft state. CSP `frame-ancestors` is set per-request when
`PUBLIC_PREVIEW_PARENT_ORIGIN` is configured so the admin iframe can
embed the response.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Peter Meier
00d42ebb42