Implement the 013-hp-status-indicators feature that adds visual HP status indicators to combatant rows with a pure domain function deriving bloodied/unconscious states

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

packages/domain/src/__tests__/hp-status.test.ts

@@ -0,0 +1,55 @@
+import { describe, expect, it } from "vitest";
+import { deriveHpStatus } from "../hp-status.js";
+
+describe("deriveHpStatus", () => {
+	it("returns healthy when currentHp >= maxHp / 2", () => {
+		expect(deriveHpStatus(10, 20)).toBe("healthy");
+		expect(deriveHpStatus(15, 20)).toBe("healthy");
+		expect(deriveHpStatus(20, 20)).toBe("healthy");
+	});
+
+	it("returns bloodied when 0 < currentHp < maxHp / 2", () => {
+		expect(deriveHpStatus(9, 20)).toBe("bloodied");
+		expect(deriveHpStatus(1, 20)).toBe("bloodied");
+		expect(deriveHpStatus(5, 20)).toBe("bloodied");
+	});
+
+	it("returns unconscious when currentHp <= 0", () => {
+		expect(deriveHpStatus(0, 20)).toBe("unconscious");
+	});
+
+	it("returns unconscious with negative HP", () => {
+		expect(deriveHpStatus(-5, 20)).toBe("unconscious");
+	});
+
+	it("returns undefined when maxHp is undefined", () => {
+		expect(deriveHpStatus(10, undefined)).toBeUndefined();
+	});
+
+	it("returns undefined when currentHp is undefined", () => {
+		expect(deriveHpStatus(undefined, 20)).toBeUndefined();
+	});
+
+	it("returns undefined when both are undefined", () => {
+		expect(deriveHpStatus(undefined, undefined)).toBeUndefined();
+	});
+
+	it("handles maxHp=1 (no bloodied state possible)", () => {
+		expect(deriveHpStatus(1, 1)).toBe("healthy");
+		expect(deriveHpStatus(0, 1)).toBe("unconscious");
+	});
+
+	it("handles maxHp=2 (1/2 is healthy, not bloodied)", () => {
+		expect(deriveHpStatus(1, 2)).toBe("healthy");
+		expect(deriveHpStatus(0, 2)).toBe("unconscious");
+	});
+
+	it("handles odd maxHp=21 (10 is bloodied since 10 < 10.5)", () => {
+		expect(deriveHpStatus(10, 21)).toBe("bloodied");
+		expect(deriveHpStatus(11, 21)).toBe("healthy");
+	});
+
+	it("returns healthy when currentHp exceeds maxHp", () => {
+		expect(deriveHpStatus(25, 20)).toBe("healthy");
+	});
+});