Implement the 025-display-initiative feature that adds initiative modifier and passive initiative display to creature stat blocks, calculated as DEX modifier + (proficiency multiplier × proficiency bonus) from bestiary data, shown in MM 2024 format on the AC line

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

apps/web/src/components/stat-block.tsx

@@ -1,4 +1,8 @@
-import type { Creature } from "@initiative/domain";
+import {
+	type Creature,
+	calculateInitiative,
+	formatInitiativeModifier,
+} from "@initiative/domain";
 
 interface StatBlockProps {
 	creature: Creature;
@@ -40,6 +44,12 @@ export function StatBlock({ creature }: StatBlockProps) {
 		{ label: "CHA", score: creature.abilities.cha },
 	];
 
+	const initiative = calculateInitiative({
+		dexScore: creature.abilities.dex,
+		cr: creature.cr,
+		initiativeProficiency: creature.initiativeProficiency,
+	});
+
 	return (
 		<div className="space-y-1 text-foreground">
 			{/* Header */}
@@ -65,6 +75,11 @@ export function StatBlock({ creature }: StatBlockProps) {
 							({creature.acSource})
 						</span>
 					)}
+					<span className="ml-3">
+						<span className="font-semibold">Initiative</span>{" "}
+						{formatInitiativeModifier(initiative.modifier)} (
+						{initiative.passive})
+					</span>
 				</div>
 				<div>
 					<span className="font-semibold">Hit Points</span>{" "}