docs: replace SHOWCASE-ROADMAP.md with docs/backlog/ (17 WPs)

Turns the prior roadmap sketch into ordered, gated work packages (enforcement
gates, FP/DDD consistency, CIBG fidelity, Storybook curriculum, a11y) from the
2026-07-02 showcase-hardening audit.

docs/backlog/WP-08-store-idiom.md

@@ -0,0 +1,70 @@
+# WP-08 — One store idiom + machine naming + TEA MDX
+
+Status: todo
+Phase: 1 — FP/DDD core
+
+## Why
+
+Docs (`docs/fp-tea-atomic-design.md`, ARCHITECTURE §2c) teach `createStore` as THE
+wiring, but the wizard pages hand-wire `signal(model)` + local `dispatch()` — juniors see
+two idioms and copy the wrong one. Machine naming also drifts:
+`change-request.machine.ts` exports bare `State`/`Msg`; `upload.machine.ts` exports
+`reduceUpload`/`initialUpload`.
+
+## Read first
+
+- `src/app/shared/application/store.ts` (`createStore`) + its spec
+- `docs/fp-tea-atomic-design.md` Part on TEA-in-Angular
+- All `*.machine.ts` files (6) and their UI wiring sites (wizard components/pages)
+
+## Decisions (pre-made, don't relitigate)
+
+- **`createStore` is THE idiom** — migrate the hand-wired pages to it. One shape
+  everywhere is the teachability win; the migration is ~5 lines per page.
+- Naming convention (goes into CLAUDE.md §3):
+  - State/Msg types are context-prefixed: `ChangeRequestState`, `ChangeRequestMsg` (rename
+    the bare ones; other machines already comply).
+  - A top-level machine exports `initial` + `reduce`.
+  - A **composable sub-machine** (embedded in a parent model) keeps prefixed value
+    exports: `initialUpload`/`reduceUpload` **stay** — prefixing avoids alias noise at
+    the composition site.
+
+## Files
+
+- `src/app/registratie/domain/change-request.machine.ts` (+ spec + consumers) — rename
+- Wizard UI wiring: `registratie-wizard.component.ts`, `intake-wizard.component.ts`,
+  `herregistratie-wizard.component.ts` (whichever hand-wire `signal`+dispatch) →
+  `createStore`
+- `CLAUDE.md` §3 — the naming + wiring convention
+- New `src/docs/machines.mdx` — title `Foundations/State Machines (TEA)`
+
+## Steps
+
+1. Rename `State`/`Msg` in change-request (mechanical; lint/build finds consumers).
+2. Swap hand-wired model signals for `createStore(initial, reduce)` in the wizard
+   components; templates keep dispatching messages — no template changes expected.
+3. Write the convention into CLAUDE.md §3 (including the sub-machine rule).
+4. MDX page: Model/Msg/reduce, commands-outside-reducers, `createStore` wiring, the
+   naming rules — linking `herregistratie.machine.ts` as the worked example.
+
+## Acceptance criteria
+
+- [ ] `grep -rn "export type State\b\|export type Msg\b" src/app` → empty.
+- [ ] Every machine consumer wires via `createStore`; no local `signal(model)` +
+      hand-rolled dispatch remains.
+- [ ] Convention documented in CLAUDE.md; MDX renders.
+- [ ] All machine specs pass unchanged (reducers untouched).
+
+## Verification
+
+GREEN + `npm run test-storybook:ci`. Smoke: all three wizards step forward/back and
+submit.
+
+## Out of scope
+
+Changing reducer logic or messages; store specs for root stores (they're covered where
+logic exists).
+
+## Risks
+
+Rename ripple — purely mechanical; reducer specs are the net.