M3: модуль сохранения

По ARCHITECTURE.md: реестр независимых секций, JSON с ключом на секцию.
Ключи — явные строковые константы, а не имена классов: релизная сборка
минифицирует имена и молча потеряла бы все сохранения.

- ISaveSection, SaveManager, IStorage + MemoryStorage
- CocosStorage: единственный файл модуля, знающий про движок;
  при отказе хранилища уходит в память, а не роняет игру
- StatsSection: сыграно/побед/поражений/ничьих, текущая и лучшая серия
- терпимая загрузка: битый JSON, чужая версия, сломанная секция
  или отвалившееся хранилище не ломают остальное
- проверка чистоты расширена на modules/ со списком адаптеров

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

docs/TECHNICAL.md

@@ -24,9 +24,11 @@ from the layers below it and never from the ones above.
   core/      pure rules and bots — no `cc` import anywhere
 ```
 
-The rule enforced by review and by the test harness: **nothing under
-`assets/scripts/core/` may import from `cc`.** It is plain TypeScript, runnable
-under Node, and that is what makes the rules testable without the engine.
+The rule, enforced by `npm run check:core-purity`: **nothing under
+`assets/scripts/core/` may import from `cc`**, and under
+`assets/scripts/modules/` only the adapters explicitly listed in that script
+may. Everything else is plain TypeScript, runnable under Node, which is what
+makes the rules and the save format testable without the engine.
 
 ## Folder map
 
@@ -49,7 +51,8 @@ assets/
       match/                  Match (stateful shell), runMatch (headless driver)
       util/                   seeded RNG, shuffle
     modules/
-      save/                   SaveManager, ISaveSection, StatsSection, storage
+      save/                   SaveManager, ISaveSection, StatsSection,
+                              IStorage + MemoryStorage, CocosStorage (engine)
     app/                      Bootstrap, ServiceLocator, SceneRouter
     ui/
       lobby/                  lobby screen controller
@@ -108,6 +111,12 @@ warning rather than failing the whole load, so a bad release cannot brick a save
 
 Keys are explicit string constants, not class names — release builds minify.
 
+The document written is `{ version, sections: { <key>: <payload> } }`. Storage
+sits behind `IStorage`, so all of the save logic is testable headlessly;
+`CocosStorage` is the only file in the module that imports the engine, and it
+falls back to an in-memory store when the device refuses to persist (private
+browsing, a full quota) rather than taking the game down.
+
 ## Conventions
 
 - TypeScript, 4-space indent, `PascalCase` for types, `camelCase` for members,