Complete module release documentation

docs/internal/validation.md

@@ -27,6 +27,19 @@ on parse or inspection errors. It runs before product checks and build callbacks
 `Request.ReadCandidateTree` lets selected file checks request candidate
 contents; the Go-only path does not enumerate the tree.
 
+## Selected validation inputs
+
+`CandidateTree` keeps the full committed repository lookup separate from the
+ordered file input set. The selected module's committed regular-file inputs
+exclude independently released nested modules, while vendored contents stay
+in scope. Explicit shared-file selections are normalized from repository-root
+paths, added as individual files, and deduplicated with module inputs by path.
+File-size exclusions are normalized from the selected module directory. Link
+resolution can still inspect a committed destination outside the selected input
+set without adding that destination's content to the checks. The public
+selection, nil/empty behavior, and profile path bases belong to the
+[configuration reference](../config.md) and the root facade's GoDoc.
+
 The workspace-file check uses that same candidate inventory and reports blob
 entries named go.work or go.work.sum, including nested paths and symlink blobs.
 It does not read workspace contents or depend on the workspace selected for Go