feat(fp): WP-08 — one store idiom + machine naming + TEA MDX

Rename change-request.machine.ts's bare State/Msg to ChangeRequestState/
ChangeRequestMsg (the last machine not context-prefixed), document the
createStore-is-the-idiom + naming convention in CLAUDE.md §3, and add the
Foundations/State Machines (TEA) curriculum page. The wizard pages already
wired createStore (confirmed by reading each and by git log) -- the WP's
"hand-wired signal(model)" premise was stale; recorded as a deviation.

src/app/registratie/domain/change-request.machine.ts

@@ -23,13 +23,13 @@ export type Errors = Partial<Record<keyof Draft, string>>;
  * Submitting/Submitted/Failed carry the parsed `Valid`. Illegal states (submitting
  * an invalid draft, a success screen with errors) are unrepresentable.
  */
-export type State =
+export type ChangeRequestState =
   | { tag: 'Editing'; draft: Draft; errors: Errors }
   | { tag: 'Submitting'; data: Valid }
   | { tag: 'Submitted'; data: Valid; referentie: string }
   | { tag: 'Failed'; data: Valid; error: string };
 
-export const initial: State = {
+export const initial: ChangeRequestState = {
   tag: 'Editing',
   draft: { straat: '', postcode: '', woonplaats: '' },
   errors: {},
@@ -51,16 +51,16 @@ function validate(draft: Draft): Result<Errors, Valid> {
   return { ok: false, error: errors };
 }
 
-export type Msg =
+export type ChangeRequestMsg =
   | { tag: 'SetField'; key: keyof Draft; value: string }
   | { tag: 'Submit' }
   | { tag: 'Retry' }
   | { tag: 'SubmitConfirmed'; referentie: string }
   | { tag: 'SubmitFailed'; error: string }
   | { tag: 'Reset' }
-  | { tag: 'Seed'; state: State }; // mount a specific state (stories/tests)
+  | { tag: 'Seed'; state: ChangeRequestState }; // mount a specific state (stories/tests)
 
-export function reduce(s: State, m: Msg): State {
+export function reduce(s: ChangeRequestState, m: ChangeRequestMsg): ChangeRequestState {
   switch (m.tag) {
     case 'SetField':
       return s.tag === 'Editing' ? { ...s, draft: { ...s.draft, [m.key]: m.value } } : s;