Implement the 017-combat-conditions feature that adds D&D 5e status conditions to combatants with icon tags, color coding, and a compact toggle picker in the encounter tracker

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

packages/domain/src/toggle-condition.ts

@@ -0,0 +1,65 @@
+import type { ConditionId } from "./conditions.js";
+import { CONDITION_DEFINITIONS, VALID_CONDITION_IDS } from "./conditions.js";
+import type { DomainEvent } from "./events.js";
+import type { CombatantId, DomainError, Encounter } from "./types.js";
+
+export interface ToggleConditionSuccess {
+	readonly encounter: Encounter;
+	readonly events: DomainEvent[];
+}
+
+export function toggleCondition(
+	encounter: Encounter,
+	combatantId: CombatantId,
+	conditionId: ConditionId,
+): ToggleConditionSuccess | DomainError {
+	if (!VALID_CONDITION_IDS.has(conditionId)) {
+		return {
+			kind: "domain-error",
+			code: "unknown-condition",
+			message: `Unknown condition "${conditionId}"`,
+		};
+	}
+
+	const targetIdx = encounter.combatants.findIndex((c) => c.id === combatantId);
+
+	if (targetIdx === -1) {
+		return {
+			kind: "domain-error",
+			code: "combatant-not-found",
+			message: `No combatant found with ID "${combatantId}"`,
+		};
+	}
+
+	const target = encounter.combatants[targetIdx];
+	const current = target.conditions ?? [];
+	const isActive = current.includes(conditionId);
+
+	let newConditions: readonly ConditionId[] | undefined;
+	let event: DomainEvent;
+
+	if (isActive) {
+		const filtered = current.filter((c) => c !== conditionId);
+		newConditions = filtered.length > 0 ? filtered : undefined;
+		event = { type: "ConditionRemoved", combatantId, condition: conditionId };
+	} else {
+		const added = [...current, conditionId];
+		const order = CONDITION_DEFINITIONS.map((d) => d.id);
+		added.sort((a, b) => order.indexOf(a) - order.indexOf(b));
+		newConditions = added;
+		event = { type: "ConditionAdded", combatantId, condition: conditionId };
+	}
+
+	const updatedCombatants = encounter.combatants.map((c) =>
+		c.id === combatantId ? { ...c, conditions: newConditions } : c,
+	);
+
+	return {
+		encounter: {
+			combatants: updatedCombatants,
+			activeIndex: encounter.activeIndex,
+			roundNumber: encounter.roundNumber,
+		},
+		events: [event],
+	};
+}