feat(entity): Chunk #4 data layer + entity UI (characters & world-building)

Data layer:
- Fuzzy scorer (packages/core/src/fuzzy.ts) with index recovery + unit tests
- Backlink computation (packages/core/src/backlinks.ts) incl. entity-level backlinks
- Consistency checker (packages/core/src/consistency.ts) incl. reciprocity/scope + unit tests
- StorageAdapter contract extended with listEntities/searchEntities/saveEntity/deleteEntity;
  implemented in Local (Dexie) and Server adapters; contract tests cover entity CRUD + ?q= search
- WorldItem.fields now supports list values (keyPeople, rivals); expanded RelationshipKind
- @mention autocomplete extension + picker in the editor package

Entity UI (apps/web/src/features/entities/):
- Generic field renderer (EntityFields) driven by ENTITY_FIELDS/FieldDef
- Tabbed directory with fuzzy search + entity cards (EntitiesView)
- Create/edit/delete drawer (EntityEditor) reusing shared fields
- Relationship editor + force-directed SVG relationship map
- Entity engine stylesheet; wired into nav

Store: project-store entity methods (load/create/update/delete) over the StorageAdapter contract.

CI-green: typecheck, lint, 65 tests, and web build all pass.

packages/core/src/autosave.test.ts

@@ -29,6 +29,16 @@ function mockAdapter(): StorageAdapter & { saved: DocumentRef[] } {
       return null;
     },
     async saveEntity() {},
+    async listEntities() {
+      return [];
+    },
+    async getEntity() {
+      return null;
+    },
+    async deleteEntity() {},
+    async searchEntities() {
+      return [];
+    },
     async saveBoard() {},
     async saveAISession() {},
     async saveDocument(doc: DocumentRef) {