Simplify: one abstract base class per layer

- BaseKVStorage / BaseEventStorage / BaseDocumentStorage define the API once;
  implementations provide only raw primitives (client and server share an API)
- Drop KV indexes, query planner, unique indexes; document stores take index fields
- Escape every char <= '/' so child keys stay contiguous; skip-scan is now simple
- Event-sourced documents = event storage + any document store for projections
- New folder layout (kv-storage, event-storage, document-storage, utils); tests only in test/

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017Qxbkp4tA7G5SCWjzWuxmE

src/index.ts

@@ -1,8 +1,18 @@
-export * from './errors.js'
-export * from './core/path.js'
-export * from './core/encoding.js'
-export * from './kv/index.js'
-export * from './types/schema.js'
-export * from './events/index.js'
-export * from './documents/index.js'
-export * from './http/index.js'
+export * from './kv-storage/base-kv-storage.js'
+export * from './kv-storage/kv-storage-in-memory.js'
+export * from './kv-storage/kv-storage-http.js'
+export * from './kv-storage/kv-storage-http-server.js'
+export * from './event-storage/base-event-storage.js'
+export * from './event-storage/event-storage-kv.js'
+export * from './document-storage/base-document-storage.js'
+export * from './document-storage/document-storage-in-memory.js'
+export * from './document-storage/document-storage-kv.js'
+export * from './document-storage/event-sourced-document-storage.js'
+export * from './utils/document-path.js'
+export * from './utils/document-query.js'
+export * from './utils/document-update.js'
+export * from './utils/errors.js'
+export * from './utils/json.js'
+export * from './utils/keys.js'
+export * from './utils/schema.js'
+export * from './utils/ulid.js'