Add player character management feature

Persistent player character templates (name, AC, HP, color, icon) with
full CRUD, bestiary-style search to add PCs to encounters with pre-filled
stats, and color/icon visual distinction in combatant rows. Also stops
the stat block panel from auto-opening when adding a creature.

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

packages/domain/src/create-player-character.ts

@@ -0,0 +1,87 @@
+import type { DomainEvent } from "./events.js";
+import type {
+	PlayerCharacter,
+	PlayerCharacterId,
+} from "./player-character-types.js";
+import {
+	VALID_PLAYER_COLORS,
+	VALID_PLAYER_ICONS,
+} from "./player-character-types.js";
+import type { DomainError } from "./types.js";
+
+export interface CreatePlayerCharacterSuccess {
+	readonly characters: readonly PlayerCharacter[];
+	readonly events: DomainEvent[];
+}
+
+export function createPlayerCharacter(
+	characters: readonly PlayerCharacter[],
+	id: PlayerCharacterId,
+	name: string,
+	ac: number,
+	maxHp: number,
+	color: string,
+	icon: string,
+): CreatePlayerCharacterSuccess | DomainError {
+	const trimmed = name.trim();
+
+	if (trimmed === "") {
+		return {
+			kind: "domain-error",
+			code: "invalid-name",
+			message: "Player character name must not be empty",
+		};
+	}
+
+	if (!Number.isInteger(ac) || ac < 0) {
+		return {
+			kind: "domain-error",
+			code: "invalid-ac",
+			message: "AC must be a non-negative integer",
+		};
+	}
+
+	if (!Number.isInteger(maxHp) || maxHp < 1) {
+		return {
+			kind: "domain-error",
+			code: "invalid-max-hp",
+			message: "Max HP must be a positive integer",
+		};
+	}
+
+	if (!VALID_PLAYER_COLORS.has(color)) {
+		return {
+			kind: "domain-error",
+			code: "invalid-color",
+			message: `Invalid color: ${color}`,
+		};
+	}
+
+	if (!VALID_PLAYER_ICONS.has(icon)) {
+		return {
+			kind: "domain-error",
+			code: "invalid-icon",
+			message: `Invalid icon: ${icon}`,
+		};
+	}
+
+	const newCharacter: PlayerCharacter = {
+		id,
+		name: trimmed,
+		ac,
+		maxHp,
+		color: color as PlayerCharacter["color"],
+		icon: icon as PlayerCharacter["icon"],
+	};
+
+	return {
+		characters: [...characters, newCharacter],
+		events: [
+			{
+				type: "PlayerCharacterCreated",
+				playerCharacterId: id,
+				name: trimmed,
+			},
+		],
+	};
+}