refactor(registratie): extract the read half of createDraftSync (RB-21)

createDraftSync mixed a read path (findConcept, load, the read half of
resume) with its write path (ensureId, flush, submit, reset) in one
187-line function -- CQ-001's finding. Move findConcept and loadConcept
into a new application/find-concept.ts as free functions that take the
adapter, so they get a direct spec with no Angular TestBed.

createDraftSync keeps the closure state (id, ensuring, resumeGate) and
the whole write path unchanged -- this is a move, not a redesign. The
resumeGate coupling that lets the write path wait for the read path
stays exactly where it was.

createDraftSync shrinks from 187 to 169 lines. draft-sync.spec.ts is
unchanged -- it never called resume()/load() directly, and its 409
recovery test for submit() still exercises the extracted findConcept
through ensureId's catch branch.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

libs/shared/docs/behaviour-spec.mdx

@@ -20,7 +20,7 @@ tested where._
 
 Every bullet below is a real test name from the suite — an `it()` title (frontend) or a test
 method name (backend), read as a sentence. Nothing here is hand-written prose: this page
-**is** the suite, reshaped for a business reader. 451 frontend behaviours across
+**is** the suite, reshaped for a business reader. 460 frontend behaviours across
 9 contexts; 236 backend behaviours across 41 test
 classes.
 
@@ -470,6 +470,14 @@ classes.
 - lists soort/waarvoor/status/referentie/ingediend, plus reason when rejected
 - reference falls back to em dash for a Concept
 
+#### findConcept
+
+- returns the id of the existing Concept of the given type
+- returns undefined when the list has no application of the given type
+- returns undefined when the matching type is not a Concept
+- returns undefined when adapter.list() resolves with an unparsable shape
+- returns undefined when adapter.list() rejects
+
 #### hasProgress
 
 - is false for a fresh wizard
@@ -486,6 +494,13 @@ classes.
 
 - derives the beroep from the chosen diploma and flags origin duo
 
+#### loadConcept
+
+- reads the draft off a Concept
+- reports a missing draft as null
+- reports not-concept when the id has moved past Concept (submitted)
+- reports not-concept when the id is unknown or deleted (detail rejects)
+
 #### manual diploma fallback
 
 - KiesHandmatig flags handmatig with the maximal question set and no beroep yet