Add advantage/disadvantage rolling for initiative

Right-click or long-press the d20 button (per-combatant or Roll All)
to open a context menu with Advantage and Disadvantage options.
Normal left-click behavior is unchanged.

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

packages/application/src/__tests__/roll-initiative-use-case.test.ts

@@ -61,7 +61,7 @@ describe("rollInitiativeUseCase", () => {
 		const result = rollInitiativeUseCase(
 			store,
 			combatantId("unknown"),
-			10,
+			[10],
 			() => undefined,
 		);
 
@@ -80,7 +80,7 @@ describe("rollInitiativeUseCase", () => {
 		const result = rollInitiativeUseCase(
 			store,
 			combatantId("Fighter"),
-			10,
+			[10],
 			() => undefined,
 		);
 
@@ -96,7 +96,7 @@ describe("rollInitiativeUseCase", () => {
 		const result = rollInitiativeUseCase(
 			store,
 			combatantId("Goblin"),
-			10,
+			[10],
 			() => undefined,
 		);
 
@@ -116,7 +116,7 @@ describe("rollInitiativeUseCase", () => {
 		const result = rollInitiativeUseCase(
 			store,
 			combatantId("Goblin"),
-			10,
+			[10],
 			(id) => (id === GOBLIN_ID ? creature : undefined),
 		);
 
@@ -124,6 +124,42 @@ describe("rollInitiativeUseCase", () => {
 		expect(requireSaved(store.saved).combatants[0].initiative).toBe(12);
 	});
 
+	it("uses higher roll with advantage", () => {
+		const creature = makeCreature();
+		const enc = encounterWithCreatureLink("Goblin", GOBLIN_ID);
+		const store = stubEncounterStore(enc);
+
+		// Dex 14 -> modifier +2, advantage picks max(5, 15) = 15, 15 + 2 = 17
+		const result = rollInitiativeUseCase(
+			store,
+			combatantId("Goblin"),
+			[5, 15],
+			(id) => (id === GOBLIN_ID ? creature : undefined),
+			"advantage",
+		);
+
+		expect(isDomainError(result)).toBe(false);
+		expect(requireSaved(store.saved).combatants[0].initiative).toBe(17);
+	});
+
+	it("uses lower roll with disadvantage", () => {
+		const creature = makeCreature();
+		const enc = encounterWithCreatureLink("Goblin", GOBLIN_ID);
+		const store = stubEncounterStore(enc);
+
+		// Dex 14 -> modifier +2, disadvantage picks min(5, 15) = 5, 5 + 2 = 7
+		const result = rollInitiativeUseCase(
+			store,
+			combatantId("Goblin"),
+			[5, 15],
+			(id) => (id === GOBLIN_ID ? creature : undefined),
+			"disadvantage",
+		);
+
+		expect(isDomainError(result)).toBe(false);
+		expect(requireSaved(store.saved).combatants[0].initiative).toBe(7);
+	});
+
 	it("applies initiative proficiency bonus correctly", () => {
 		// CR 5 -> PB 3, dex 16 -> mod +3, initiativeProficiency 1
 		// modifier = 3 + 1*3 = 6, roll 8 + 6 = 14
@@ -145,7 +181,7 @@ describe("rollInitiativeUseCase", () => {
 		const result = rollInitiativeUseCase(
 			store,
 			combatantId("Monster"),
-			8,
+			[8],
 			(id) => (id === GOBLIN_ID ? creature : undefined),
 		);