Use useOptimistic for instant source manager cache clearing

Source rows disappear immediately when cleared instead of waiting
for the IndexedDB operation to complete. Real state syncs after.

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

apps/web/src/components/source-manager.tsx

@@ -1,5 +1,5 @@
 import { Database, Trash2 } from "lucide-react";
-import { useCallback, useEffect, useState } from "react";
+import { useCallback, useEffect, useOptimistic, useState } from "react";
 import type { CachedSourceInfo } from "../adapters/bestiary-cache.js";
 import * as bestiaryCache from "../adapters/bestiary-cache.js";
 import { Button } from "./ui/button.js";
@@ -10,6 +10,16 @@ interface SourceManagerProps {
 
 export function SourceManager({ onCacheCleared }: SourceManagerProps) {
 	const [sources, setSources] = useState<CachedSourceInfo[]>([]);
+	const [optimisticSources, applyOptimistic] = useOptimistic(
+		sources,
+		(
+			state,
+			action: { type: "remove"; sourceCode: string } | { type: "clear" },
+		) =>
+			action.type === "clear"
+				? []
+				: state.filter((s) => s.sourceCode !== action.sourceCode),
+	);
 
 	const loadSources = useCallback(async () => {
 		const cached = await bestiaryCache.getCachedSources();
@@ -21,18 +31,20 @@ export function SourceManager({ onCacheCleared }: SourceManagerProps) {
 	}, [loadSources]);
 
 	const handleClearSource = async (sourceCode: string) => {
+		applyOptimistic({ type: "remove", sourceCode });
 		await bestiaryCache.clearSource(sourceCode);
 		await loadSources();
 		onCacheCleared();
 	};
 
 	const handleClearAll = async () => {
+		applyOptimistic({ type: "clear" });
 		await bestiaryCache.clearAll();
 		await loadSources();
 		onCacheCleared();
 	};
 
-	if (sources.length === 0) {
+	if (optimisticSources.length === 0) {
 		return (
 			<div className="flex flex-col items-center gap-2 py-8 text-center">
 				<Database className="h-8 w-8 text-muted-foreground" />
@@ -57,7 +69,7 @@ export function SourceManager({ onCacheCleared }: SourceManagerProps) {
 				</Button>
 			</div>
 			<ul className="flex flex-col gap-1">
-				{sources.map((source) => (
+				{optimisticSources.map((source) => (
 					<li
 						key={source.sourceCode}
 						className="flex items-center justify-between rounded-md border border-border px-3 py-2"