Add PF2e persistent damage condition tags

Persistent damage displayed as compact tags with damage type icon and
formula (e.g., Flame + "2d6"). Supports fire, bleed, acid, cold,
electricity, poison, and mental types. One instance per type, added via
sub-picker in the condition picker. PF2e only, persists across reload.

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

packages/domain/src/persistent-damage.ts

@@ -0,0 +1,165 @@
+import type { DomainEvent } from "./events.js";
+import {
+	type CombatantId,
+	type DomainError,
+	type Encounter,
+	findCombatant,
+	isDomainError,
+} from "./types.js";
+
+export const PERSISTENT_DAMAGE_TYPES = [
+	"fire",
+	"bleed",
+	"acid",
+	"cold",
+	"electricity",
+	"poison",
+	"mental",
+] as const;
+
+export type PersistentDamageType = (typeof PERSISTENT_DAMAGE_TYPES)[number];
+
+export const VALID_PERSISTENT_DAMAGE_TYPES: ReadonlySet<string> = new Set(
+	PERSISTENT_DAMAGE_TYPES,
+);
+
+export interface PersistentDamageEntry {
+	readonly type: PersistentDamageType;
+	readonly formula: string;
+}
+
+export interface PersistentDamageDefinition {
+	readonly type: PersistentDamageType;
+	readonly label: string;
+	readonly iconName: string;
+	readonly color: string;
+}
+
+export const PERSISTENT_DAMAGE_DEFINITIONS: readonly PersistentDamageDefinition[] =
+	[
+		{ type: "fire", label: "Fire", iconName: "Flame", color: "orange" },
+		{ type: "bleed", label: "Bleed", iconName: "Droplets", color: "red" },
+		{
+			type: "acid",
+			label: "Acid",
+			iconName: "FlaskConical",
+			color: "lime",
+		},
+		{ type: "cold", label: "Cold", iconName: "Snowflake", color: "sky" },
+		{
+			type: "electricity",
+			label: "Electricity",
+			iconName: "Zap",
+			color: "yellow",
+		},
+		{
+			type: "poison",
+			label: "Poison",
+			iconName: "Droplet",
+			color: "green",
+		},
+		{
+			type: "mental",
+			label: "Mental",
+			iconName: "BrainCog",
+			color: "pink",
+		},
+	];
+
+export interface PersistentDamageSuccess {
+	readonly encounter: Encounter;
+	readonly events: DomainEvent[];
+}
+
+function applyPersistentDamage(
+	encounter: Encounter,
+	combatantId: CombatantId,
+	newEntries: readonly PersistentDamageEntry[] | undefined,
+): Encounter {
+	return {
+		combatants: encounter.combatants.map((c) =>
+			c.id === combatantId ? { ...c, persistentDamage: newEntries } : c,
+		),
+		activeIndex: encounter.activeIndex,
+		roundNumber: encounter.roundNumber,
+	};
+}
+
+export function addPersistentDamage(
+	encounter: Encounter,
+	combatantId: CombatantId,
+	damageType: PersistentDamageType,
+	formula: string,
+): PersistentDamageSuccess | DomainError {
+	if (!VALID_PERSISTENT_DAMAGE_TYPES.has(damageType)) {
+		return {
+			kind: "domain-error",
+			code: "unknown-damage-type",
+			message: `Unknown persistent damage type "${damageType}"`,
+		};
+	}
+	if (formula.trim().length === 0) {
+		return {
+			kind: "domain-error",
+			code: "empty-formula",
+			message: "Persistent damage formula must not be empty",
+		};
+	}
+
+	const found = findCombatant(encounter, combatantId);
+	if (isDomainError(found)) return found;
+	const { combatant: target } = found;
+	const current = target.persistentDamage ?? [];
+
+	// Replace existing entry of same type, or append
+	const filtered = current.filter((e) => e.type !== damageType);
+	const newEntries = [
+		...filtered,
+		{ type: damageType, formula: formula.trim() },
+	];
+
+	// Sort by definition order
+	const order = PERSISTENT_DAMAGE_DEFINITIONS.map((d) => d.type);
+	newEntries.sort((a, b) => order.indexOf(a.type) - order.indexOf(b.type));
+
+	return {
+		encounter: applyPersistentDamage(encounter, combatantId, newEntries),
+		events: [
+			{
+				type: "PersistentDamageAdded",
+				combatantId,
+				damageType,
+				formula: formula.trim(),
+			},
+		],
+	};
+}
+
+export function removePersistentDamage(
+	encounter: Encounter,
+	combatantId: CombatantId,
+	damageType: PersistentDamageType,
+): PersistentDamageSuccess | DomainError {
+	const found = findCombatant(encounter, combatantId);
+	if (isDomainError(found)) return found;
+	const { combatant: target } = found;
+	const current = target.persistentDamage ?? [];
+
+	if (!current.some((e) => e.type === damageType)) {
+		return {
+			kind: "domain-error",
+			code: "persistent-damage-not-active",
+			message: `Persistent ${damageType} damage is not active`,
+		};
+	}
+
+	const filtered = current.filter((e) => e.type !== damageType);
+	return {
+		encounter: applyPersistentDamage(
+			encounter,
+			combatantId,
+			filtered.length > 0 ? filtered : undefined,
+		),
+		events: [{ type: "PersistentDamageRemoved", combatantId, damageType }],
+	};
+}