Document main-relative companion loading

docs/internal/imports.md

@@ -20,6 +20,11 @@ patterns to discovered names, and form a set union of matching candidates across
 overlapping roots. Exclusions are applied as set difference after discovery and
 candidate normalization. They do not suppress discovery or resource errors.
 
+Layered assembly passes the resolved main context to underlay acquisition,
+replacing tier-local identity state. Contextless bindings prepare declaration
+policies and assemble the declaring payload without opening access or inventing
+selection evidence. Selected contexts use the normal acquisition and handle path.
+
 Directory traversal tracks canonical directories on the active traversal path.
 It adds an identity when descending and removes it when the frame is popped, so
 only a back-edge to an active directory is a traversal cycle; a later alias is