refactor: rename config dir to lyrathorpe and host labels

Move ./emmathorpe -> ./lyrathorpe (git mv preserves history) and rename the MBP/X1 nixosConfiguration names to lyrathorpe-mbp / lyrathorpe-x1c. The EDaaS host keeps its emmathorpe-edaas name and Emma Thorpe identity; it still imports the shared (renamed) config dir.

Derivation outputs are byte-identical to before; pure relabel.

lyrathorpe/home/shell.nix

@@ -0,0 +1,50 @@
+# Interactive shell: zsh + tmux. Wanted on every host.
+{ lib, ... }:
+{
+  programs.zsh = {
+    enable = true;
+    enableCompletion = true;
+    enableVteIntegration = true;
+    autosuggestion.enable = true;
+    historySubstringSearch.enable = true;
+    history.append = true;
+    oh-my-zsh = {
+      enable = true;
+      plugins = [
+        "git"
+        "man"
+        "history-substring-search"
+      ];
+      theme = "robbyrussell";
+    };
+    syntaxHighlighting.enable = true;
+    # Prefix the prompt with the hostname over SSH. The graphical autostart
+    # (exec sway on tty1) lives in ./desktop.nix so it never runs on headless
+    # hosts.
+    initContent = lib.mkOrder 1500 ''
+      if [ "$SSH_CLIENT" ] || [ "$SSH_TTY" ]; then
+        export PS1="%M $PS1"
+      fi
+    '';
+    envExtra = ''
+      alias cls=clear
+    '';
+  };
+
+  programs.tmux = {
+    enable = true;
+    reverseSplit = true;
+    terminal = "tmux-direct";
+    newSession = true;
+    keyMode = "vi";
+    historyLimit = 50000;
+    mouse = true;
+    extraConfig = ''
+      # Alt+Arrow pane navigation
+      bind -n M-Left select-pane -L
+      bind -n M-Right select-pane -R
+      bind -n M-Up select-pane -U
+      bind -n M-Down select-pane -D
+    '';
+  };
+}