I might have some insights to offer regarding your query.
Although you haven't specified the version of Meteor you are using, I am assuming it is either version 1.4 or 1.4.0.1. It appears that these particular versions of Meteor are experiencing problems with sourcemaps for Typescript files due to multiple transpilation steps. The root cause of this issue is yet to be determined (whether it is related to Meteor or the Typescript compiler package). Here is a relevant GitHub issue link: https://github.com/barbatus/typescript/issues/23
UPDATE: The reported issue has been resolved.
As a temporary solution, I recommend reverting back to a 1.3.x.x version of Meteor. For projects like the Socially tutorial, you can specify the Meteor release during creation by using the following command:
$ meteor create --release 1.3.5.1 Socially
(you can find a list of releases at: https://github.com/meteor/meteor/releases)
The 'app.html' and 'app.html!raw' files are produced by the meteor angular compilers to address issues with using templateUrl and the meteor build process. It is recommended to either include inline templates or import templates as shown below:
// This import statement loads the content of the html file into 'template'
import template from './app.html';
@Component({
selector: 'app',
// Instead of templateUrl, use:
template, // <--- 'template,' is shorthand for: 'template: template,'
directives ... etc.
The import syntax may seem unconventional, but it is made possible by the meteor angular pre-compiler that converts each html and css file into corresponding js files. This process explains the presence of the peculiar app.html and app.html!raw files.
The unusual characters in the initial 'app' folder appear to be a glitch. Meteor attempts to insert a computer emoji, but this sometimes results in an incorrect display. It is unclear whether this issue stems from Chrome, ChromeDevTools, or Meteor itself. Personally, I believe it would be best to abandon the use of emojis in this context.