fix: handle template as a normal tag

packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js

@@ -439,7 +439,7 @@ export function RegularElement(node, context) {
 
 		// The same applies if it's a `<template>` element, since we need to
 		// set the value of `hydrate_node` to `node.content`
-		if (name === 'template') {
+		if (name === 'template' && !context.state.analysis.custom_renderer) {
 			needs_reset = true;
 			child_state.init.push(b.stmt(b.call('$.hydrate_template', arg)));
 			arg = b.member(arg, 'content');

packages/svelte/tests/custom-renderers/samples/template/_config.js

@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	html: '<template><p>hello world</p></template>'
+});

packages/svelte/tests/custom-renderers/samples/template/main.svelte

@@ -0,0 +1,7 @@
+<script lang="ts">
+	let greet = $state('hello world');
+</script>
+
+<template>
+	<p>{greet}</p>
+</template>