fix: ensure jsx does not reference server entrypoint (#4203)

Co-authored-by: Nate Moore <nate@astro.build>

.changeset/slimy-parrots-exist.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Ensure JSX does not reference server entrypoint

packages/astro/src/jsx/babel.ts

@@ -1,9 +1,10 @@
 import type { PluginObj } from '@babel/core';
 import * as t from '@babel/types';
 import { pathToFileURL } from 'node:url';
-import { ClientOnlyPlaceholder } from '../runtime/server/index.js';
 import type { PluginMetadata } from '../vite-plugin-astro/types';
 
+const ClientOnlyPlaceholder = 'astro-client-only';
+
 function isComponent(tagName: string) {
 	return (
 		(tagName[0] && tagName[0].toLowerCase() !== tagName[0]) ||

packages/astro/src/runtime/server/index.ts

@@ -34,8 +34,6 @@ import { Renderer } from './render/index.js';
 
 import { addAttribute } from './render/index.js';
 
-export const ClientOnlyPlaceholder = 'astro-client-only';
-
 // Used in creating the component. aka the main export.
 export function createComponent(cb: AstroComponentFactory) {
 	// Add a flag to this callback to mark it as an Astro component

packages/astro/src/runtime/server/jsx.ts

@@ -2,7 +2,6 @@
 import { SSRResult } from '../../@types/astro.js';
 import { AstroJSX, isVNode } from '../../jsx-runtime/index.js';
 import {
-	ClientOnlyPlaceholder,
 	escapeHTML,
 	HTMLString,
 	markHTMLString,
@@ -14,6 +13,8 @@ import {
 	voidElementNames,
 } from './index.js';
 
+const ClientOnlyPlaceholder = 'astro-client-only';
+
 const skipAstroJSXCheck = new WeakSet();
 let originalConsoleError: any;
 let consoleFilterRefs = 0;