Lay Pure out as a core with the parts selected around it

The app model, the tree store and the HTTP host lived in
prototypes/connections among the earlier document runtime, the store was
known only by its format's name, and Vega compiled six Pure sources by path.
Now, as the README's principle has it:

  core/   runtime, flow and the app model (module*.c), with what the core
          asks of storage (state.h, store.h)
  store/  the tree store (PURETRE3, PUREREC1)
  serve/  pure-serve: HTTP host, outbound delivery, JSON in place
  cli/    pure-run, pure-edit-module

A top-level make builds libpure.a (app model and store, for hosts to link)
and the hosts; make check runs the store's and the app model's tests. The
earlier runtime still builds from prototypes/connections against core/ and
store/ (check, check-tree and check-core pass). Design 009 records the rule:
parts by role behind libraries; git repositories split by coupling, so the
store stays here while its contract moves with the core, and Vega stays apart.

1 files changed, 1 insertions, 1 deletions

diff --git a/docs/research/073-single-file-persistent-tree.md b/docs/research/073-single-file-persistent-tree.md
index 13884e3..4386e93 100644
--- a/docs/research/073-single-file-persistent-tree.md
+++ b/docs/research/073-single-file-persistent-tree.md
@@ -74,7 +74,7 @@ Ctrl+S부터 저장 완료 프레임까지 잰다. 1 MiB 문서, 저장소별 3�
 
 ## 검증
 
-[`test-tree-store.c`](../../prototypes/connections/test-tree-store.c)는 ASan·UBSan에서도 통과했다.
+[`test-tree-store.c`](../../store/test-tree-store.c)는 ASan·UBSan에서도 통과했다.
 
 - 4개 키에 6,000회 무작위 편집을 평면 배열 오라클과 매번 비교했다(최대 333,510 B, 높이 2).
   매 편집 뒤 저장된 모든 비루트 노드가 기준 이상으로 채워졌는지 확인했다.