feat(search): wire SmartModeToggle into SearchFilterBar (#739)

Add smartMode $bindable plus onSmartSearch/onModeToggle callbacks. The
toggle pill sits in the input's right slot (decorative icon moved to the
left); smart mode disables the live oninput keyword search, adds
maxlength=500, and submits the NL query on Enter. 4 integration specs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/routes/SearchFilterBar.svelte

@@ -3,6 +3,7 @@ import PersonTypeahead from '$lib/person/PersonTypeahead.svelte';
 import TagInput from '$lib/tag/TagInput.svelte';
 import DateInput from '$lib/shared/primitives/DateInput.svelte';
 import SortDropdown from '$lib/shared/primitives/SortDropdown.svelte';
+import SmartModeToggle from './search/SmartModeToggle.svelte';
 import { slide } from 'svelte/transition';
 import { m } from '$lib/paraglide/messages.js';
 
@@ -20,12 +21,15 @@ let {
 	sort = $bindable('DATE'),
 	dir = $bindable('desc'),
 	showAdvanced = $bindable(false),
+	smartMode = $bindable(false),
 	initialSenderName = '',
 	initialReceiverName = '',
 	navKey = 0,
 	isLoading = false,
 	onSearch,
 	onSearchImmediate,
+	onSmartSearch,
+	onModeToggle,
 	onfocus,
 	onblur
 }: {
@@ -42,16 +46,28 @@ let {
 	sort?: string;
 	dir?: string;
 	showAdvanced?: boolean;
+	smartMode?: boolean;
 	initialSenderName?: string;
 	initialReceiverName?: string;
 	navKey?: number;
 	isLoading?: boolean;
 	onSearch: () => void;
 	onSearchImmediate?: () => void;
+	onSmartSearch?: () => void;
+	onModeToggle?: () => void;
 	onfocus?: () => void;
 	onblur?: () => void;
 } = $props();
 
+// In smart mode the keyword search must not fire on every keystroke — the NL
+// query is submitted only on Enter (or an explicit button click).
+function onSearchKeydown(event: KeyboardEvent) {
+	if (smartMode && event.key === 'Enter') {
+		event.preventDefault();
+		onSmartSearch?.();
+	}
+}
+
 // Plain (non-reactive) flag — not $state, so no reactive assignment inside $effect
 let sortDirMounted = false;
 
@@ -76,14 +92,20 @@ $effect(() => {
 			<input
 				type="text"
 				bind:value={q}
-				oninput={onSearch}
+				oninput={smartMode ? undefined : onSearch}
+				onkeydown={onSearchKeydown}
 				onfocus={onfocus}
 				onblur={onblur}
+				maxlength={smartMode ? 500 : undefined}
 				aria-label={m.docs_search_placeholder()}
 				placeholder={m.docs_search_placeholder()}
-				class="block w-full border-line py-2.5 pr-10 pl-3 placeholder-ink-3 shadow-sm focus:outline-none focus-visible:ring-2 focus-visible:ring-focus-ring"
+				class="block w-full border-line py-2.5 pl-10 placeholder-ink-3 shadow-sm focus:outline-none focus-visible:ring-2 focus-visible:ring-focus-ring {smartMode
+					? 'pr-28'
+					: 'pr-20'}"
 			/>
-			<div class="pointer-events-none absolute inset-y-0 right-0 flex items-center pr-3">
+			<!-- Decorative search icon / loading spinner — left slot keeps the right
+			     slot free for the always-visible smart-mode toggle pill. -->
+			<div class="pointer-events-none absolute inset-y-0 left-0 flex items-center pl-3">
 				{#if isLoading}
 					<svg
 						role="status"
@@ -110,6 +132,7 @@ $effect(() => {
 					/>
 				{/if}
 			</div>
+			<SmartModeToggle bind:smartMode={smartMode} onToggle={onModeToggle} />
 		</div>
 
 		<!-- Sort Dropdown -->

frontend/src/routes/search/SmartModeToggle.svelte.spec.ts

@@ -1,10 +1,13 @@
-import { describe, expect, it, afterEach } from 'vitest';
+import { describe, expect, it, vi, afterEach } from 'vitest';
 import { cleanup, render } from 'vitest-browser-svelte';
 import { page } from 'vitest/browser';
 import SmartModeToggle from './SmartModeToggle.svelte';
+import SearchFilterBar from '../SearchFilterBar.svelte';
 
 afterEach(() => cleanup());
 
+const SEARCH_PLACEHOLDER = 'Titel, Personen, Tags durchsuchen…';
+
 describe('SmartModeToggle', () => {
 	it('renders aria-pressed="false" by default and toggles on click', async () => {
 		render(SmartModeToggle, { smartMode: false });
@@ -34,3 +37,45 @@ describe('SmartModeToggle', () => {
 		await expect.element(btn).toHaveClass(/bg-primary/);
 	});
 });
+
+describe('SmartModeToggle inside SearchFilterBar', () => {
+	it('adds maxlength="500" to the search input only in smart mode', async () => {
+		render(SearchFilterBar, { onSearch: vi.fn(), sort: 'DATE', dir: 'desc', smartMode: true });
+		await expect
+			.element(page.getByPlaceholder(SEARCH_PLACEHOLDER))
+			.toHaveAttribute('maxlength', '500');
+	});
+
+	it('omits maxlength from the search input in keyword mode', async () => {
+		render(SearchFilterBar, { onSearch: vi.fn(), sort: 'DATE', dir: 'desc', smartMode: false });
+		await expect
+			.element(page.getByPlaceholder(SEARCH_PLACEHOLDER))
+			.not.toHaveAttribute('maxlength');
+	});
+
+	it('does not fire the keyword search on input while in smart mode', async () => {
+		const onSearch = vi.fn();
+		render(SearchFilterBar, { onSearch, sort: 'DATE', dir: 'desc', smartMode: true });
+		await page.getByPlaceholder(SEARCH_PLACEHOLDER).fill('Walter im Krieg');
+		expect(onSearch).not.toHaveBeenCalled();
+	});
+
+	it('fires the smart search callback on Enter in smart mode', async () => {
+		const onSmartSearch = vi.fn();
+		render(SearchFilterBar, {
+			onSearch: vi.fn(),
+			onSmartSearch,
+			sort: 'DATE',
+			dir: 'desc',
+			smartMode: true
+		});
+		const input = page.getByPlaceholder(SEARCH_PLACEHOLDER);
+		await input.fill('Walter im Krieg');
+		await input.click();
+		// Enter submits the NL query in smart mode
+		(document.activeElement as HTMLElement).dispatchEvent(
+			new KeyboardEvent('keydown', { key: 'Enter', bubbles: true })
+		);
+		await vi.waitFor(() => expect(onSmartSearch).toHaveBeenCalled());
+	});
+});