Add maintained consumer migration examples

docs/roadmap/implementation.md

@@ -1437,7 +1437,56 @@ Acceptance:
 
 ## Stage 20 — Prove consumer ergonomics and migration contracts
 
-Status: pending.
+Status: complete.
+
+Completion evidence (2026-09-06):
+
+- Added the maintained [`examples/consumers`](../../examples/consumers) package and
+  sanitized local fixtures for four application shapes. The Narratio-like example
+  uses fresh defaults, partial imports, artifacts, recorded inherited defaults, and
+  an application model profile distinct from an optional ConfigKit profile. The
+  Notarius-like example uses canonical object bindings, a string version rule,
+  dynamic options, and range-checked `int64` conversion at the runtime boundary.
+- Added WeatherReporter-like defaults-only and file loads, report maps, canonical
+  module objects, typed option unions, and shared loaded/constructed validation.
+  Application validation—not the ConfigKit schema—rejects explicit empty module and
+  path-template lists and null required module options. Recorded normalization acts
+  on detached values without mutating caller-owned constructed options. Added
+  independent ordered Seriatim-like speaker and autocorrect rule loaders while
+  retaining matching/replacement algorithms in the example package.
+- Added executable examples for all four shapes and a WeatherReporter-shaped startup
+  flow. The startup explicitly renders `SecretsReport`, demonstrates an existing
+  empty variable blocking its file and a separate successful disposable lookup,
+  translates only an explicitly set `--units` flag into an `Override`, and renders
+  its explanation. It verifies ordinary `Load` preserves the process environment
+  and never uses a real credential.
+- Generalized the assigned Narratio inspection/default/artifact outcomes and
+  WeatherReporter defaults, explicit-empty, loaded/constructed consistency, and
+  option-normalization cases. [`docs/internal/extraction.md`](../internal/extraction.md)
+  records the rechecked clean revisions, adapted cases, intentional differences,
+  and no-copy boundaries for Narratio `b68435128be1e24b94fc7ec259d6e9093669fd99`,
+  WeatherReporter `5d306a202471e10fe98923a1df27d0b0fce5c666`, Notarius
+  `77ae132e5609916da40dcd4fcc749c000a63cbac`, and Seriatim
+  `0fc92f364316c874d366b00cdc884a33e1900b25`. No sibling checkout is a build or test
+  dependency.
+- Added negative migration fixtures for integer versions, string module shorthand,
+  explicit empty lists, explicit null required options, and strict unknown fields.
+  They fail with stable `version.type`, `decode.type`, `validate.error`, and
+  `decode.unknown_field` classifications at semantic paths without parser text.
+  Dynamic options bind directly without YAML reserialization or a generic subtree
+  conversion API.
+- Added the [consumer adoption guide](../consumers/README.md), current canonical
+  module-options contract, README navigation, and component inventory. The guide
+  maps every feature-roadmap API sketch to an executable example or focused test,
+  describes removed plumbing versus retained domain code, and lists explicit
+  empty/null, object, version, integer, strict-YAML, environment-overlay, CLI, and
+  secret-reference migrations without claiming downstream repositories are migrated.
+- Confirmed the example package directly imports only ConfigKit and the standard
+  library, then reviewed the exported surface and existing AST import-boundary test
+  for aliases, generic constraints, callbacks, record fields, and safe error chains.
+  Verified `go test ./...`, `go test -race ./...`, `go vet ./...`, `go build ./...`,
+  `go mod tidy -diff`, and `git diff --check` with Go 1.26.7 on linux/amd64. No
+  deviations were required; broader hardening remains later work.
 
 Read: feature consumer-fit table, module options, external values, and both criteria.