Add min/max hit point variants for D&D creatures

A D&D stat block opened for a combatant now offers a Min/Avg/Max toggle
below the Hit Points line, deriving both ends from the Hit Dice formula
(3d6 + 6 -> 9 / 16 / 24). The switch is applied as a delta, so manual HP
edits and damage already taken survive it. Unlike the PF2e weak/elite
adjustment this is a convenience tool, not a rules mechanic: nothing but
HP changes and the combatant is not renamed. The toggle is hidden when
the HP field carries prose instead of a dice pool.

Also extracts a SegmentedControl primitive. Game system, theme and the
PF2e weak/elite toggle were three hand-rolled copies of the same markup,
which is why the D&D toggle first came out chunkier and in the wrong
accent color. All four now share one definition, and segments expose
aria-pressed instead of signalling the active state by color alone.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

packages/application/src/index.ts

@@ -27,6 +27,7 @@ export { setAcUseCase } from "./set-ac-use-case.js";
 export { setConditionValueUseCase } from "./set-condition-value-use-case.js";
 export { setCrUseCase } from "./set-cr-use-case.js";
 export { setHpUseCase } from "./set-hp-use-case.js";
+export { setHpVariantUseCase } from "./set-hp-variant-use-case.js";
 export { setInitiativeUseCase } from "./set-initiative-use-case.js";
 export { setSideUseCase } from "./set-side-use-case.js";
 export { setTempHpUseCase } from "./set-temp-hp-use-case.js";

packages/application/src/set-hp-variant-use-case.ts

@@ -0,0 +1,21 @@
+import {
+	type CombatantId,
+	type DomainError,
+	type DomainEvent,
+	type HpRange,
+	type HpVariant,
+	setHpVariant,
+} from "@initiative/domain";
+import type { EncounterStore } from "./ports.js";
+import { runEncounterAction } from "./run-encounter-action.js";
+
+export function setHpVariantUseCase(
+	store: EncounterStore,
+	combatantId: CombatantId,
+	variant: HpVariant | undefined,
+	range: HpRange,
+): DomainEvent[] | DomainError {
+	return runEncounterAction(store, (encounter) =>
+		setHpVariant(encounter, combatantId, variant, range),
+	);
+}