docs: simplify code comments, keep the detail in the README

The registry / multi-user / portable-home rationale lives in the README
(Users, Hosts, Portable home); the corresponding code comments are reduced
to one-liners that point there. No functional change (host derivations are
unchanged).

users/emmathorpe/work.nix

@@ -1,7 +1,5 @@
-# Home-manager module for the work (EDaaS/WSL) profile: corporate work toolchain
-# packages and tmux tweaks. Imported only by the work host. The corporate git
-# identity (email + signing key) is the emmathorpe entry in the identity
-# registry (users/registry.nix), applied by the shared home/git.nix.
+# Work (EDaaS/WSL) home profile: corporate toolchain + tmux tweaks. Git identity
+# comes from the registry (users/registry.nix), not here.
 { pkgs, lib, ... }:
 
 {