Decode typed configuration over defaults

docs/internal/overview.md

@@ -7,18 +7,21 @@ module and package documentation boundary. Its implemented public primitives are
 - detached provenance and diagnostic record types with empty `Metadata` queries;
 - canonical, control-safe diagnostic rendering and structured `LoadError` access;
 - opaque file, byte, reader, and no-input source construction and bounded reads;
-- a parser-independent ordered tree in `internal/document`; and
+- a parser-independent ordered tree in `internal/document`;
 - the sole upstream YAML integration in `internal/yaml`, which translates validated
-  input into that owned tree and exposes no parser types outside its boundary; and
+  input into that owned tree and exposes no parser types outside its boundary;
 - a per-operation private reflection descriptor graph in `schema.go` for supported
   types, YAML field binding, inlining, secret tags, recursion, and semantic paths;
-  and
 - descriptor-driven canonical projection, detached typed cloning, cycle/limit
-  enforcement, and structural comparison in `projection.go`.
+  enforcement, and structural comparison in `projection.go`; and
+- strict schema-driven decoding over detached defaults in `decode.go`, including
+  mapping/sequence semantics, null and numeric policy, safe codec errors, presence,
+  baseline/final trees, and initial default/input origins.
 
-The [configuration contract](../config.md) owns implemented input, schema, and
-ownership behavior. ConfigKit intentionally exposes no typed loading or decoding API yet.
-Private metadata population will be integrated when that lifecycle exists.
+The [configuration contract](../config.md) owns implemented input, schema, decoding,
+and ownership behavior. ConfigKit intentionally exposes no typed loading API yet;
+the decoder and its initial metadata artifacts remain private until that lifecycle
+exists.
 
 The source-extraction inventory records the application foundations assigned to
 future implementation work: