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/contexts/adapter-context.tsx

@@ -0,0 +1,38 @@
+import { createContext, type ReactNode, useContext } from "react";
+import type {
+	BestiaryCachePort,
+	BestiaryIndexPort,
+	EncounterPersistence,
+	PlayerCharacterPersistence,
+	UndoRedoPersistence,
+} from "../adapters/ports.js";
+
+export interface Adapters {
+	encounterPersistence: EncounterPersistence;
+	undoRedoPersistence: UndoRedoPersistence;
+	playerCharacterPersistence: PlayerCharacterPersistence;
+	bestiaryCache: BestiaryCachePort;
+	bestiaryIndex: BestiaryIndexPort;
+}
+
+const AdapterContext = createContext<Adapters | null>(null);
+
+export function AdapterProvider({
+	adapters,
+	children,
+}: {
+	adapters: Adapters;
+	children: ReactNode;
+}) {
+	return (
+		<AdapterContext.Provider value={adapters}>
+			{children}
+		</AdapterContext.Provider>
+	);
+}
+
+export function useAdapters(): Adapters {
+	const ctx = useContext(AdapterContext);
+	if (!ctx) throw new Error("useAdapters requires AdapterProvider");
+	return ctx;
+}