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/edit-player-character.ts

@@ -0,0 +1,137 @@
+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 EditPlayerCharacterSuccess {
+	readonly characters: readonly PlayerCharacter[];
+	readonly events: DomainEvent[];
+}
+
+interface EditFields {
+	readonly name?: string;
+	readonly ac?: number;
+	readonly maxHp?: number;
+	readonly color?: string;
+	readonly icon?: string;
+}
+
+function validateFields(fields: EditFields): DomainError | null {
+	if (fields.name !== undefined && fields.name.trim() === "") {
+		return {
+			kind: "domain-error",
+			code: "invalid-name",
+			message: "Player character name must not be empty",
+		};
+	}
+	if (
+		fields.ac !== undefined &&
+		(!Number.isInteger(fields.ac) || fields.ac < 0)
+	) {
+		return {
+			kind: "domain-error",
+			code: "invalid-ac",
+			message: "AC must be a non-negative integer",
+		};
+	}
+	if (
+		fields.maxHp !== undefined &&
+		(!Number.isInteger(fields.maxHp) || fields.maxHp < 1)
+	) {
+		return {
+			kind: "domain-error",
+			code: "invalid-max-hp",
+			message: "Max HP must be a positive integer",
+		};
+	}
+	if (fields.color !== undefined && !VALID_PLAYER_COLORS.has(fields.color)) {
+		return {
+			kind: "domain-error",
+			code: "invalid-color",
+			message: `Invalid color: ${fields.color}`,
+		};
+	}
+	if (fields.icon !== undefined && !VALID_PLAYER_ICONS.has(fields.icon)) {
+		return {
+			kind: "domain-error",
+			code: "invalid-icon",
+			message: `Invalid icon: ${fields.icon}`,
+		};
+	}
+	return null;
+}
+
+function applyFields(
+	existing: PlayerCharacter,
+	fields: EditFields,
+): PlayerCharacter {
+	return {
+		id: existing.id,
+		name: fields.name !== undefined ? fields.name.trim() : existing.name,
+		ac: fields.ac !== undefined ? fields.ac : existing.ac,
+		maxHp: fields.maxHp !== undefined ? fields.maxHp : existing.maxHp,
+		color:
+			fields.color !== undefined
+				? (fields.color as PlayerCharacter["color"])
+				: existing.color,
+		icon:
+			fields.icon !== undefined
+				? (fields.icon as PlayerCharacter["icon"])
+				: existing.icon,
+	};
+}
+
+export function editPlayerCharacter(
+	characters: readonly PlayerCharacter[],
+	id: PlayerCharacterId,
+	fields: EditFields,
+): EditPlayerCharacterSuccess | DomainError {
+	const index = characters.findIndex((c) => c.id === id);
+	if (index === -1) {
+		return {
+			kind: "domain-error",
+			code: "player-character-not-found",
+			message: `Player character not found: ${id}`,
+		};
+	}
+
+	const validationError = validateFields(fields);
+	if (validationError) return validationError;
+
+	const existing = characters[index];
+	const updated = applyFields(existing, fields);
+
+	if (
+		updated.name === existing.name &&
+		updated.ac === existing.ac &&
+		updated.maxHp === existing.maxHp &&
+		updated.color === existing.color &&
+		updated.icon === existing.icon
+	) {
+		return {
+			kind: "domain-error",
+			code: "no-changes",
+			message: "No fields changed",
+		};
+	}
+
+	const newList = characters.map((c, i) => (i === index ? updated : c));
+
+	return {
+		characters: newList,
+		events: [
+			{
+				type: "PlayerCharacterUpdated",
+				playerCharacterId: id,
+				oldName: existing.name,
+				newName: updated.name,
+			},
+		],
+	};
+}