Batch bestiary add produces a single undo entry

Extract addOneFromBestiary (no undo) and build addMultipleFromBestiary
on top so confirming N creatures from the bestiary panel creates one
undo entry that restores the entire batch, not N individual entries.

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

apps/web/src/components/__tests__/turn-navigation.test.tsx

@@ -52,6 +52,7 @@ function mockContext(overrides: Partial<Encounter> = {}) {
 		toggleCondition: vi.fn(),
 		toggleConcentration: vi.fn(),
 		addFromBestiary: vi.fn(),
+		addMultipleFromBestiary: vi.fn(),
 		addFromPlayerCharacter: vi.fn(),
 		makeStore: vi.fn(),
 		withUndo: vi.fn((action: () => unknown) => action()),