refactor(wpcarro): Remove briefcase references

TL;DR:
- prefer WPCARRO env-var to BRIEFCASE
- remove repository URLs from Emacs libraries
- prefer tvl-depot-path where possible
- reduce the scope of constants.el
- prune (some not all) stale CI configuration

Change-Id: I21e9130402502ec6fa2fc4b46753c890069be62d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/4545
Tested-by: BuildkiteCI
Reviewed-by: wpcarro <wpcarro@gmail.com>

users/wpcarro/boilerplate/README.md

@@ -10,7 +10,7 @@ Let's say that you would like to create a game for
 following:
 
 ```shell
-$ cp ~/briefcase/boilerplate/typescript ~/briefcase/website/sandbox/game
+$ cp -r typescript path/to/new-project
 ```
 
 This initializes the project. To start developing, run:

users/wpcarro/boilerplate/clojure/README.md

@@ -7,7 +7,7 @@ This boilerplate uses `lein` to manage the project.
 To use this boilerplate, run the following in a shell:
 
 ```shell
-$ cp ~/briefcase/boilerplate/clojure path/to/new-project
+$ cp -r . path/to/new-project
 ```
 
 After running the above command, change the following files to remove the