Complete relative import destination documentation audit

docs/internal/overview.md

@@ -9,8 +9,9 @@ Implemented component owners:
 
 - `internal/engine` owns host and native-filesystem source acquisition,
   grouped strict composition, recursive precedence assembly, per-input mapping
-  placement within that assembly, and destination-local sibling inheritance
-  before typed decoding. It retains source placement alongside physical source
+  placement and immediate-parent-relative import placement within that
+  assembly, and destination-local sibling inheritance before typed decoding.
+  It retains each source's effective placement alongside physical source
   identity and owns schema
   inspection, lifecycle coordination, callback auditing,
   provenance/history, passive source-context retention, secret resolution and
@@ -53,4 +54,5 @@ decision; [ADR 0011](../adr/0011-input-destinations.md) records the placement
 decision. See the [development guide](../development.md) for validation commands
 and [release procedure](../release.md) for source-candidate gates. [ADR
 0009](../adr/0009-sibling-inheritance.md) records why inheritance is a built-in
-post-assembly structural operation.
+post-assembly structural operation. [ADR 0012](../adr/0012-relative-import-destinations.md)
+records the relative-import extension.