Bundle still has import statements for Lit

[datvm]

• Version: 3.4.5
• Rollup Version: 4.1.5
• Operating System and version (if applicable): Windows 11
• Node Version (if applicable): v18.16.1
• Does it work with tsc (if applicable): yes

Reproduction

I am trying to bundle material-components/material-web so I cloned it there and added rollup and rollup-plugin-ts and nothing else:

    "rollup": "^4.1.5",
    "rollup-plugin-ts": "^3.4.5",

Running rollup -c is successful and all is packed except Lit components. These are the result files:

// all.bundled.js
import { customElement, property, state, query, queryAssignedElements, queryAll, queryAsync, queryAssignedNodes } from 'lit/decorators.js';
import { LitElement, html, css, isServer, nothing, render } from 'lit';
import { classMap } from 'lit/directives/class-map.js';
import { literal, html as html$1 } from 'lit/static-html.js';
import { styleMap } from 'lit/directives/style-map.js';
import { when } from 'lit/directives/when.js';
import { live } from 'lit/directives/live.js';

// Other content...

// all.bundled.d.ts
import { LitElement, ReactiveElement, PropertyValues, TemplateResult, nothing, ReactiveController, ReactiveControllerHost } from "lit";
import { ClassInfo } from "lit/directives/class-map.js";
import { StaticValue } from "lit/static-html.js";

// License info

declare const internals: unique symbol;
// Others

This is my rollup.config.js:

import ts from "rollup-plugin-ts";

const config = [
  {
    input: "./all.ts",
    output: [{
      file: "./catalog/dist/all.bundled.js",
      format: "esm",
    }],
    plugins: [
      ts({
        tsconfig: "tsconfig.json",
      }),
    ],
  },
];

export default config;

Expected Behavior

Everything should be contained within the bundled file. No import statement should be there.

Actual Behavior

import statements at the beginning of the file. I also tried switching to @rollup/plugin-typescript and it gives the same result as well, all references to Lit are kept with import.