Remove demo combatants and allow empty encounters

Empty encounters are now valid (INV-1 updated). New sessions start
with zero combatants instead of pre-populated Aria/Brak/Cael.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/hooks/use-encounter.ts

@@ -22,7 +22,6 @@ import type {
 } from "@initiative/domain";
 import {
 	combatantId,
-	createEncounter,
 	isDomainError,
 	creatureId as makeCreatureId,
 	resolveCreatureName,
@@ -33,24 +32,16 @@ import {
 	saveEncounter,
 } from "../persistence/encounter-storage.js";
 
-function createDemoEncounter(): Encounter {
-	const result = createEncounter([
-		{ id: combatantId("1"), name: "Aria" },
-		{ id: combatantId("2"), name: "Brak" },
-		{ id: combatantId("3"), name: "Cael" },
-	]);
-
-	if (isDomainError(result)) {
-		throw new Error(`Failed to create demo encounter: ${result.message}`);
-	}
-
-	return result;
-}
+const EMPTY_ENCOUNTER: Encounter = {
+	combatants: [],
+	activeIndex: 0,
+	roundNumber: 1,
+};
 
 function initializeEncounter(): Encounter {
 	const stored = loadEncounter();
 	if (stored !== null) return stored;
-	return createDemoEncounter();
+	return EMPTY_ENCOUNTER;
 }
 
 function deriveNextId(encounter: Encounter): number {