Merge branch 'refactor-node' into refactor-node-next

Forward-merge the dataplane/session concept-home reorganization onto
the next line. The moved files carry next's (XX-line) content; the one
hand-resolved surface is src/peer/active.rs, where the source-location
citation sits in different surrounding text than on the master line —
resolved by keeping next's body and applying the same node/session.rs
-> node/session/mod.rs citation update.

src/node/mod.rs

@@ -7,6 +7,7 @@
 pub(crate) mod acl;
 mod bloom;
 pub(crate) mod context;
+mod dataplane;
 #[cfg(unix)]
 pub(crate) mod decrypt_worker;
 #[cfg(unix)]