Use combobox for target type selector, refresh previews on change

- Replace toggle buttons with <select> dropdown for target type
- Add refreshAllPreviews() that immediately re-renders all open
  previews when target type changes (no 800ms debounce)
- validateSlot() now accepts optional immediate flag

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

frontend/src/routes/template-configs/+page.svelte

@@ -28,7 +28,7 @@
 	let slotErrorTypes = $state<Record<string, string>>({});
 	let validateTimers: Record<string, ReturnType<typeof setTimeout>> = {};
 
-	function validateSlot(slotKey: string, template: string) {
+	function validateSlot(slotKey: string, template: string, immediate = false) {
 		// Clear previous timer
 		if (validateTimers[slotKey]) clearTimeout(validateTimers[slotKey]);
 		if (!template) {
@@ -40,8 +40,7 @@
 			return;
 		}
 
-		// Debounce 800ms
-		validateTimers[slotKey] = setTimeout(async () => {
+		const doValidate = async () => {
 			try {
 				const res = await api('/template-configs/preview-raw', { method: 'POST', body: JSON.stringify({ template, target_type: previewTargetType }) });
 				slotErrors = { ...slotErrors, [slotKey]: res.error || '' };
@@ -60,7 +59,21 @@
 				slotErrorLines = { ...slotErrorLines, [slotKey]: null };
 				slotErrorTypes = { ...slotErrorTypes, [slotKey]: '' };
 			}
-		}, 800);
+		};
+		if (immediate) { doValidate(); }
+		else { validateTimers[slotKey] = setTimeout(doValidate, 800); }
+	}
+
+	function refreshAllPreviews() {
+		// Re-validate and re-preview all slots that have content (immediate, no debounce)
+		for (const group of templateSlots) {
+			for (const slot of group.slots) {
+				const template = (form as any)[slot.key];
+				if (template && slot.key !== 'date_format') {
+					validateSlot(slot.key, template, true);
+				}
+			}
+		}
 	}
 
 	const defaultForm = () => ({
@@ -181,17 +194,12 @@
 
 		<!-- Target type selector for preview -->
 		<div class="flex items-center gap-2">
-			<label class="text-sm font-medium">{t('templateConfig.previewAs')}:</label>
-			<div class="flex gap-1">
-				<button type="button" onclick={() => previewTargetType = 'telegram'}
-					class="px-3 py-1 text-xs rounded-md transition-colors {previewTargetType === 'telegram' ? 'bg-[var(--color-primary)] text-[var(--color-primary-foreground)]' : 'bg-[var(--color-muted)] text-[var(--color-muted-foreground)]'}">
-					Telegram
-				</button>
-				<button type="button" onclick={() => previewTargetType = 'webhook'}
-					class="px-3 py-1 text-xs rounded-md transition-colors {previewTargetType === 'webhook' ? 'bg-[var(--color-primary)] text-[var(--color-primary-foreground)]' : 'bg-[var(--color-muted)] text-[var(--color-muted-foreground)]'}">
-					Webhook
-				</button>
-			</div>
+			<label for="preview-target" class="text-sm font-medium">{t('templateConfig.previewAs')}:</label>
+			<select id="preview-target" bind:value={previewTargetType} onchange={refreshAllPreviews}
+				class="px-2 py-1 border border-[var(--color-border)] rounded-md text-sm bg-[var(--color-background)]">
+				<option value="telegram">Telegram</option>
+				<option value="webhook">Webhook</option>
+			</select>
 		</div>
 
 		{#each templateSlots as group}