fix(wpcarro/nix): Remove <briefcase> references

Angle-bracketed references are a Nix anti-pattern, and thankfully this
repository enforces this as a standard.

TL;DR:
- Drop angle-bracketed references
- Change `briefcase` -> `users.wpcarro`
- Fix any resulting regressions
- Fix //users/wpcarro/tools/simple_vim
- Mark //users/wpcarro/boilerplate/typescript and related projects
  as broken
- drop .skip-subtree file, enabling depot CI

Change-Id: I7153cbabafa617bfd6b199370cbec65cb75441f6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/4325
Tested-by: BuildkiteCI
Reviewed-by: wpcarro <wpcarro@gmail.com>
Reviewed-by: tazjin <mail@tazj.in>
Reviewed-by: grfn <grfn@gws.fyi>
Autosubmit: wpcarro <wpcarro@gmail.com>

users/wpcarro/emacs/default.nix

@@ -2,7 +2,7 @@
 
 let
   inherit (builtins) path;
-  inherit (depot.third_party) emacsPackagesGen emacs27;
+  inherit (depot.third_party.nixpkgs) emacsPackagesGen emacs27;
   inherit (pkgs) writeShellScript writeShellScriptBin;
   inherit (pkgs.lib.strings) concatStringsSep makeBinPath;
 
@@ -49,7 +49,6 @@ let
       clipmon # TODO: Prefer an Emacs client for clipmenud.
       evil
       evil-collection
-      evil-magit
       evil-commentary
       evil-surround
       key-chord
@@ -103,7 +102,6 @@ let
       eglot
       dap-mode
       lsp-ui
-      company-lsp
       suggest
       paradox
       flymake-shellcheck