Document shared source version checks

docs/internal/overview.md

@@ -10,7 +10,8 @@ Implemented component owners:
 - `internal/engine` owns host and native-filesystem source acquisition,
   grouped strict composition, recursive precedence assembly, per-input mapping
   placement and immediate-parent-relative import placement within that
-  assembly, and destination-local sibling inheritance before typed decoding.
+  assembly, destination-local sibling inheritance before typed decoding, and
+  shared source-version checking with sanitized declaration evidence.
   It retains each source's effective placement alongside physical source
   identity and owns schema
   inspection, lifecycle coordination, callback auditing,
@@ -44,7 +45,8 @@ these constraints and rejects exported aliases, fields, or signatures involving
 internal types.
 
 The [configuration contract](../config.md) owns implemented YAML and lifecycle
-semantics, including [input destinations](../config.md#input-destinations) and
+semantics, including [input destinations](../config.md#input-destinations),
+[shared source-version checks](../config.md#shared-source-version-checks), and
 [effective configuration diffs](../config.md#effective-configuration-diffs).
 The [consumer adoption guide](../consumers/README.md) owns application guidance.
 The [architecture policy](../policy/architecture.md) owns contributor
@@ -55,4 +57,5 @@ 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. [ADR 0012](../adr/0012-relative-import-destinations.md)
-records the relative-import extension.
+records the relative-import extension; [ADR 0013](../adr/0013-shared-source-version-checks.md)
+records the source-version decision.