feat(fp): WP-05 — parse-don't-validate closure + MDX

Close the three remaining unvalidated `as <DomainType>` casts at the wire
boundary (intake-policy, big-register aantekening type, brief passage scope),
each replaced by a Result-returning parser with a rejection-case spec, plus
the Foundations/Parse, don't validate curriculum page.

docs/backlog/WP-05-parse-boundaries.md

@@ -1,6 +1,6 @@
 # WP-05 — Parse-don't-validate closure + MDX
 
-Status: todo
+Status: done
 Phase: 1 — FP/DDD core
 
 ## Why
@@ -45,10 +45,10 @@ PassageScope` → validated parse (the file is otherwise parse-heavy; this one f
 
 ## Acceptance criteria
 
-- [ ] No unvalidated `as <DomainType>` casts in `**/infrastructure/**` (the sanctioned
+- [x] No unvalidated `as <DomainType>` casts in `**/infrastructure/**` (the sanctioned
       "narrow unknown to `Partial<Dto>` then parse" entry-cast is fine).
-- [ ] Each new parser has a spec including a rejection case.
-- [ ] MDX renders under Foundations in Storybook.
+- [x] Each new parser has a spec including a rejection case.
+- [x] MDX renders under Foundations in Storybook.
 
 ## Verification