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/hooks/use-encounter.ts

@@ -298,9 +298,10 @@ export function useEncounter() {
 		setEvents((prev) => [...prev, ...result]);
 	}, [makeStore]);
 
-	const addFromBestiary = useCallback(
-		(entry: BestiaryIndexEntry): CreatureId | null => {
-			const snapshot = encounterRef.current;
+	const addOneFromBestiary = useCallback(
+		(
+			entry: BestiaryIndexEntry,
+		): { cId: CreatureId; events: DomainEvent[] } | null => {
 			const store = makeStore();
 			const existingNames = store.get().combatants.map((c) => c.name);
 			const { newName, renames } = resolveCreatureName(
@@ -328,8 +329,20 @@ export function useEncounter() {
 				creatureId: cId,
 			});
 
-			if (isDomainError(result)) {
-				store.save(snapshot);
+			if (isDomainError(result)) return null;
+
+			return { cId, events: result };
+		},
+		[makeStore],
+	);
+
+	const addFromBestiary = useCallback(
+		(entry: BestiaryIndexEntry): CreatureId | null => {
+			const snapshot = encounterRef.current;
+			const added = addOneFromBestiary(entry);
+
+			if (!added) {
+				makeStore().save(snapshot);
 				return null;
 			}
 
@@ -337,10 +350,36 @@ export function useEncounter() {
 			undoRedoRef.current = newState;
 			setUndoRedoState(newState);
 
-			setEvents((prev) => [...prev, ...result]);
-			return cId;
+			setEvents((prev) => [...prev, ...added.events]);
+			return added.cId;
 		},
-		[makeStore],
+		[makeStore, addOneFromBestiary],
+	);
+
+	const addMultipleFromBestiary = useCallback(
+		(entry: BestiaryIndexEntry, count: number): CreatureId | null => {
+			const snapshot = encounterRef.current;
+			const allEvents: DomainEvent[] = [];
+			let lastCId: CreatureId | null = null;
+
+			for (let i = 0; i < count; i++) {
+				const added = addOneFromBestiary(entry);
+				if (!added) {
+					makeStore().save(snapshot);
+					return null;
+				}
+				allEvents.push(...added.events);
+				lastCId = added.cId;
+			}
+
+			const newState = pushUndo(undoRedoRef.current, snapshot);
+			undoRedoRef.current = newState;
+			setUndoRedoState(newState);
+
+			setEvents((prev) => [...prev, ...allEvents]);
+			return lastCId;
+		},
+		[makeStore, addOneFromBestiary],
 	);
 
 	const addFromPlayerCharacter = useCallback(
@@ -426,6 +465,7 @@ export function useEncounter() {
 		toggleCondition,
 		toggleConcentration,
 		addFromBestiary,
+		addMultipleFromBestiary,
 		addFromPlayerCharacter,
 		undo: undoAction,
 		redo: redoAction,