Introduce adapter injection and migrate test suite

Replace direct adapter/persistence imports with context-based injection
(AdapterContext + useAdapters) so tests use in-memory implementations
instead of vi.mock. Migrate component tests from context mocking to
AllProviders with real hooks. Extract export/import logic from ActionBar
into useEncounterExportImport hook. Add bestiary-cache and
bestiary-index-adapter test suites. Raise adapter coverage thresholds
(68→80 lines, 56→62 branches).

77 test files, 891 tests, all passing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/src/adapters/bestiary-cache.ts

@@ -5,7 +5,7 @@ const DB_NAME = "initiative-bestiary";
 const STORE_NAME = "sources";
 const DB_VERSION = 2;
 
-export interface CachedSourceInfo {
+interface CachedSourceInfo {
 	readonly sourceCode: string;
 	readonly displayName: string;
 	readonly creatureCount: number;