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/configs/install

@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
 
-configs="$BRIEFCASE/configs"
+configs="$WPCARRO/configs"
 
 (cd "$configs" && stow --target="$HOME" .)

users/wpcarro/configs/uninstall

@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
 
-configs="$BRIEFCASE/configs"
+configs="$WPCARRO/configs"
 
 (cd "$configs" && stow --delete --target="$HOME" .)