Atomic addCombatant with optional CombatantInit bag

addCombatant now accepts an optional init parameter for pre-filled stats
(HP, AC, initiative, creatureId, color, icon, playerCharacterId), making
combatant creation a single atomic operation with domain validation.

This eliminates the multi-step store.save() bypass in addFromBestiary and
addFromPlayerCharacter, and removes the CombatantOpts/applyCombatantOpts
helpers. Also extracts shared initiative sort logic into initiative-sort.ts
used by both addCombatant and setInitiative.

Closes #15

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

packages/application/src/add-combatant-use-case.ts

@@ -1,6 +1,7 @@
 import {
 	addCombatant,
 	type CombatantId,
+	type CombatantInit,
 	type DomainError,
 	type DomainEvent,
 	isDomainError,
@@ -11,9 +12,10 @@ export function addCombatantUseCase(
 	store: EncounterStore,
 	id: CombatantId,
 	name: string,
+	init?: CombatantInit,
 ): DomainEvent[] | DomainError {
 	const encounter = store.get();
-	const result = addCombatant(encounter, id, name);
+	const result = addCombatant(encounter, id, name, init);
 
 	if (isDomainError(result)) {
 		return result;