feat: restore old toolchain button

web/src/routes/+page.svelte

@@ -2,8 +2,40 @@
 	import { getTool } from '$lib/registry';
 	import ToolPage from '$lib/components/ToolPage.svelte';
 	import ToolSearch from '$lib/components/search/ToolSearch.svelte';
+	import Button from '$lib/components/ui/Button.svelte';
+
+	const LAST_TOOL_KEY = 'last-tool-id';
+
+	function loadLastToolId(): string | null {
+		if (typeof localStorage === 'undefined') return null;
+		try {
+			const id = localStorage.getItem(LAST_TOOL_KEY);
+			return id !== null && getTool(id) ? id : null;
+		} catch {
+			return null;
+		}
+	}
 
 	let selectedId = $state<string | null>(null);
+	let restoreOnOpen = $state(false);
+	let lastToolId = $state<string | null>(loadLastToolId());
+
+	function openTool(id: string, restore = false) {
+		if (!getTool(id)) return;
+		selectedId = id;
+		restoreOnOpen = restore;
+		lastToolId = id;
+		if (typeof localStorage === 'undefined') return;
+		try {
+			localStorage.setItem(LAST_TOOL_KEY, id);
+		} catch {
+			// приватный режим — просто не запоминаем
+		}
+	}
+
+	function closeTool() {
+		selectedId = null;
+	}
 
 	let selected = $derived(selectedId !== null ? (getTool(selectedId) ?? null) : null);
 </script>
@@ -18,15 +50,23 @@
 	<section class="hero">
 		<h1>Что делаем с изображением?</h1>
 		<p class="lead text-muted">Найдите инструмент — все операции выполняются локально в браузере.</p>
-		<ToolSearch onSelect={(id) => (selectedId = id)} />
+		<ToolSearch onSelect={(id) => openTool(id)} />
+		{#if lastToolId !== null && getTool(lastToolId)}
+			{@const restoreId = lastToolId}
+			<div class="restore-row">
+				<Button variant="secondary" fullWidth onclick={() => openTool(restoreId, true)}>
+					↩ Вернуть последний: {getTool(restoreId)?.title}
+				</Button>
+			</div>
+		{/if}
 	</section>
 {:else}
 	<section class="workbench">
-		<button type="button" class="back text-caption text-muted" onclick={() => (selectedId = null)}>
+		<button type="button" class="back text-caption text-muted" onclick={closeTool}>
 			← Сменить инструмент
 		</button>
 		{#key selectedId}
-			<ToolPage tool={selected} />
+			<ToolPage tool={selected} restoreChain={restoreOnOpen} />
 		{/key}
 	</section>
 {/if}
@@ -46,6 +86,11 @@
 		margin: 0 auto var(--space-4);
 	}
 
+	.restore-row {
+		max-width: 36rem;
+		margin: var(--space-2) auto 0;
+	}
+
 	.back {
 		display: inline-block;
 		margin-bottom: var(--space-3);