docs: record ZB.MOM.WW.Configuration fleet-wide adoption + add design/plan

Configuration is now adopted across all three sister apps (local branches),
so flip the status lines in CLAUDE.md, components/configuration/GAPS.md, and the
lib README/CLAUDE.md from 'not adopted' to adopted (also corrects 27->42 tests).
Adds the brainstorm design doc + bite-sized implementation plan (+tasks.json)
under docs/plans/ that drove the adoption.

components/configuration/GAPS.md

@@ -1,12 +1,14 @@
 # Configuration validation — gaps & adoption backlog
 
 Divergence of each project from [`spec/SPEC.md`](spec/SPEC.md), and the ordered backlog to adopt
-the shared `ZB.MOM.WW.Configuration` library. The library is **BUILT @ 0.1.0** (27 tests) at
-[`../../ZB.MOM.WW.Configuration/`](../../ZB.MOM.WW.Configuration/) but **NOT YET ADOPTED** by any
-app — so every item below is an *adoption* item, not a library-build item. This mirrors the Auth /
-UI-Theme / Health pattern: the shared library is built first; adoption is opt-in and tracked here,
-not forced. (Unlike the observability pass, there is **no in-pass sister-repo adoption** in this
-release.)
+the shared `ZB.MOM.WW.Configuration` library. The library is **BUILT @ 0.1.0** (42 tests) at
+[`../../ZB.MOM.WW.Configuration/`](../../ZB.MOM.WW.Configuration/) and was **ADOPTED across all three
+apps on 2026-06-01** — published to the Gitea feed, then consumed on each repo's local default branch
+(merged, **not yet pushed** to remotes). The adoption items below are now largely closed: MxGateway +
+ScadaBridge migrated to `OptionsValidatorBase`/`AddValidatedOptions` behaviour-preservingly (validator
+messages byte-identical), ScadaBridge's `StartupValidator` → `ConfigPreflight`, and OtOpcUa gained
+net-new `Ldap`/`OpcUa` validators (plus a follow-on pass: real `Security:Ldap` binding, `ValidateOnStart`
+wired for ScadaBridge Cluster/HealthMonitoring, and assorted hardening).
 
 Status legend: ⛔ gap · 🟡 partial · ✅ matches.