src/vs/workbench/contrib/notebook/common/notebookEditorInput.ts/NotebookEditorInput/capabilities
class NotebookEditorInput:	override get capabilities(): EditorInputCapabilities {
		let capabilities = EditorInputCapabilities.None;

		if (this.resource.scheme === Schemas.untitled) {
			capabilities |= EditorInputCapabilities.Untitled;
		}

		if (this._editorModelReference) {
			if (this._editorModelReference.object.isReadonly()) {
				capabilities |= EditorInputCapabilities.Readonly;
			}
		} else {
			if (this.fileService.hasCapability(this.resource, FileSystemProviderCapabilities.Readonly)) {
				capabilities |= EditorInputCapabilities.Readonly;
			}
		}

		return capabilities;
	}