fix(site-publish): close split migration boundaries

Authored-By: OpenAI (GPT-5) <noreply@openai.com>

README.md

@@ -133,10 +133,18 @@ any route's mutable objects change.
 Mutable default and override partitions receive their final cache policy before
 the matching prefix-scoped stale deletion, so publication never exposes a
 provisional cache policy or a pointer to a missing immutable target.
+Generated Ingress annotations retain each bucket's prior route and immutable paths. When a move
+places that retired prefix inside the new sync scope, only its declared
+immutable subtrees are excluded; a current-file collision fails publication.
+The bucket-keyed history rejects a protected-to-public transition even when the
+artifact is renamed; publishing that artifact publicly requires a new bucket.
+Legacy single-surface is public for this downgrade check. Removing or renaming
+an immutable rule preserves its prior URLs; current mutable content at one of
+those paths is rejected instead of replacing it.
 
 Artifact input directories must be pairwise disjoint after filesystem
 resolution. Publication stops before build or upload if one contains another or
-escapes the repository. Descendant symlinks are also rejected, preventing
+escapes the repository. Symlinked roots, components, and descendants are also rejected, preventing
 protected input from entering a public artifact through dereference. Split
 storage endpoints are pinned to Garage, and each website
 authority is derived from its bucket; a site cannot expose an arbitrary backend.