Fails with cannot find npm module, despite it being listed in package.json & builds correctly

[samdoeswork]

Describe the bug
Trying to setup storybook for angular, one of my components imports an npm module like so:

import * as monaco from "monaco-editor";

The failure is:
Module not found: Error: Can't resolve 'monaco-editor' in 'C:\apps\jaf\client\src\app\components\ui\ui-monaco'

It's definitely in the package.json, and angular builds fine.

Here's tsconfig.app.json:

{
"extends": "../tsconfig.base.json",
"compilerOptions": {
"outDir": "../out-tsc/app",
"module": "es2020",
"baseUrl": "src",
"types": [],
"experimentalDecorators": true
},
"files": [
"main.ts",
"polyfills.ts"
],
"exclude": [
"/*.stories.ts",
"/.stories."
]
}