feat(tmux): apply dotfiles tmux config

From emmaisadev/dotfiles (tmux.conf): run a non-login shell
(default-command), drop the stock %/" split keys (the s/v vim splits
already come from reverseSplit), declare foot's terminal-features
(RGB/sync/clipboard/title/ccolour/cstyle), and raise the scrollback to
500000. Alt-arrow pane nav and mouse were already present. Also drop a
stale comment referencing the removed tty1 autostart.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lyrathorpe/home/shell.nix

@@ -31,9 +31,7 @@
       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.
+    # Prefix the prompt with the hostname over SSH.
     initContent = lib.mkOrder 1500 ''
       if [ "$SSH_CLIENT" ] || [ "$SSH_TTY" ]; then
         export PS1="%M $PS1"
@@ -50,14 +48,33 @@
     terminal = "tmux-direct";
     newSession = true;
     keyMode = "vi";
-    historyLimit = 50000;
+    historyLimit = 500000;
     mouse = true;
+    # `reverseSplit = true` already binds s -> vertical and v -> horizontal
+    # split (the dotfiles' vim-style splits).
     extraConfig = ''
+      # Run a non-login shell in new panes/windows.
+      set -g default-command "''${SHELL}"
+
+      # Drop the stock split keys in favour of the s/v binds above.
+      unbind %
+      unbind '"'
+
       # 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
+
+      # Tell tmux which capabilities the foot terminal supports, so truecolor,
+      # synchronised output, the system clipboard (OSC 52), window titles and
+      # cursor styling all pass through.
+      set -as terminal-features ",foot*:RGB"
+      set -as terminal-features ",foot*:sync"
+      set -as terminal-features ",foot*:clipboard"
+      set -as terminal-features ",foot*:title"
+      set -as terminal-features ",foot*:ccolour"
+      set -as terminal-features ",foot*:cstyle"
     '';
   };
 }