Document and demonstrate native and layered configuration loading

docs/roadmap/deferred.md

@@ -11,11 +11,13 @@ General environment-variable configuration overlays are not supported. Typed sec
 references and explicit directory bootstrap are the environment convention. Literal
 credential configuration and implicit secret-directory discovery are unsupported.
 
-The initial release deliberately excludes:
+The following remain deliberately excluded:
 
 - automatic `conf.d` discovery;
 - remote imports, arbitrary providers, and additional configuration formats;
-- custom merge strategies, sequence merging, reset operators, and overlay inheritance;
+- custom merge strategies, sequence merging, and reset operators;
+- named overlay inheritance, tracked separately in the
+  [PromptKit inheritance request](feature-request-promptkit-inheritance.md);
 - parser-specific or custom structural-decoding extension APIs;
 - generic dynamic-subtree conversion and module-registry APIs;
 - automatic schema migrations;

docs/roadmap/implementation.md

@@ -506,6 +506,16 @@ unchanged final tree. Benchmarks run with `-benchmem` and parameterized sizes.
 
 ## Stage 10: Complete consumer examples and architecture documentation
 
+**Completed 2026-09-29.** Maintained executable examples now cover a simple
+embedded filesystem source and a layered catalog with imported embedded defaults,
+a mapping underlay, an independent host main file, explicit false/zero values,
+domain validation, and resource access through the retained origin's source ID.
+The configuration contract, public declaration comments, consumer/development
+guides, README, component overview, architecture/deferred text, roadmap status,
+and draft ADR status links reflect implemented behavior. Named inheritance remains
+separate and deferred; the ADRs remain drafts. The everyday checker and full race
+suite passed. No release preparation or publication was performed.
+
 1. Add a maintained simple native-filesystem example and a combined example with
    embedded defaults, two underlay tiers, independently located main input,
    programmatic contributions, and a relative resource from a retained origin.

docs/roadmap/sources-and-layering.md

@@ -1,8 +1,9 @@
 # Filesystem Sources and Source-Backed Underlays
 
-Status: agreed target for implementation; not implemented. This document owns
-the desired behavior and design rationale. The [implementation plan](implementation.md)
-owns API signatures, sequential work, and validation commands.
+Status: implemented; draft ADRs remain pending review. This document preserves
+the design target and rationale, including its historical baseline. The
+[configuration contract](../config.md) owns current behavior, and the
+[implementation plan](implementation.md) records sequential work and validation.
 
 ## Purpose and priorities
 
@@ -36,7 +37,7 @@ The [named-inheritance request](feature-request-promptkit-inheritance.md) remain
 separate and optional. This roadmap neither implements it nor adds speculative
 infrastructure for it.
 
-## Current baseline
+## Planning baseline (historical)
 
 Planning baseline: `ec26591b275bd74f89120bdea69c5f6459dfcafb`, following v0.4.2.
 Current behavior is owned by the [configuration contract](../config.md), not by