feat(work): load kube-tmux from a pinned flake input

kube-tmux is not in nixpkgs, so add the upstream repo as a flake = false
input and reference ${inputs.kube-tmux}/kube.tmux directly. The script is now
always in the store, so the previous $HOME/code/kube-tmux existence guard is
removed and the tmux status line no longer depends on a manual checkout.

Refs #50

users/emmathorpe/work.nix

@@ -1,6 +1,11 @@
 # Work (EDaaS/WSL) home profile: corporate toolchain + tmux tweaks. Git identity
 # comes from the registry (users/registry.nix), not here.
-{ pkgs, lib, ... }:
+{
+  pkgs,
+  lib,
+  inputs,
+  ...
+}:
 
 {
   # Host-scoped extras for this machine only (the EDaaS/WSL host).
@@ -47,10 +52,10 @@
     docker = "/run/current-system/sw/bin/docker";
   };
   programs.tmux = {
-    # kube-tmux is an external checkout; guard on its presence so the status
-    # line degrades gracefully (no per-refresh error) when it isn't cloned.
+    # kube context/namespace in the status line. kube-tmux is pinned as a flake
+    # input (it is not in nixpkgs), so the script is always present in the store.
     extraConfig = ''
-      set -g status-right "#(if [ -f $HOME/code/kube-tmux/kube.tmux ]; then /run/current-system/sw/bin/bash $HOME/code/kube-tmux/kube.tmux 250 red black; fi)"
+      set -g status-right "#(${pkgs.bash}/bin/bash ${inputs.kube-tmux}/kube.tmux 250 red black)"
     '';
   };
   programs.go = {