screen: that a policy was held kept across a swap of the document

Review 4, F12: `Screening::of` started screening over when the document was swapped (a
drop, a switch, a rejoin), the root pin alone carried on, so whether the document had
held a policy (`policed`, 1211) was forgotten there too, not only across a restart as
documented: after a drop with the policy removed meanwhile, late changes written under
it went in unjudged again.

It is carried on now, as the root pin is; what belongs to the old document (changes
waiting, refusals, drops held) still starts over. access.md says so.

1 files changed, 2 insertions, 2 deletions

diff --git a/docs/access.md b/docs/access.md
index 3d4aeaf..402f1ab 100644
--- a/docs/access.md
+++ b/docs/access.md
@@ -346,8 +346,8 @@ the signatures of what was written under a policy requiring them. While neither
 its document nor what it receives holds a policy, it judges only that a root is the
 epoch's, and nothing costs more than applying the changes. A policy removed, or
 replaced by one the node doesn't know, still judges what was written under it and
-comes late, as long as the node runs (after a restart, a document without a policy
-is judged as one that never had one).
+comes late, as long as the node runs, its document swapped meanwhile or not (after a
+restart, a document without a policy is judged as one that never had one).
 
 An epoch's root is pinned. A remake's is its epoch's ID, the hash of its snapshot. The
 first epoch's is its genesis change, which its genesis node logs (`The swarm's root`)