feat(nixos): migrate system configuration

configs/nixos/modules/shell/tmux/extra.conf

@@ -0,0 +1,43 @@
+# Copy-mode selections land in the system clipboard via the terminal's own
+# OSC52 escape sequence.
+set -g set-clipboard on
+
+bind -T copy-mode-vi v send -X begin-selection
+bind -T copy-mode-vi y send -X copy-selection-and-cancel
+bind -T copy-mode-vi MouseDragEnd1Pane send -X copy-selection-and-cancel
+
+# \ splits the pane side-by-side, - splits it stacked.
+# Both open the new pane in the current pane's directory, as does c for a new window.
+unbind %
+unbind '"'
+bind \\ split-window -h -c "#{pane_current_path}"
+bind - split-window -v -c "#{pane_current_path}"
+bind c new-window -c "#{pane_current_path}"
+
+bind h select-pane -L
+bind j select-pane -D
+bind k select-pane -U
+bind l select-pane -R
+
+set -g renumber-windows on
+
+bind r source-file ~/.config/tmux/tmux.conf \; display-message "tmux.conf reloaded"
+
+# Advertise RGB (true-color) capability for every terminal type.
+set -ag terminal-overrides ",*:RGB"
+
+# monitor-bell flags a background window in the status bar when it rings the
+# terminal bell while unfocused.
+# bell-action=none suppresses the actual BEL (no beep or flash).
+# The per-window status highlight is independent of it.
+setw -g monitor-bell on
+set -g bell-action none
+
+# Minimal status bar: session name plus window list only.
+# Colours are left to Stylix.
+set -g status-position bottom
+set -g status-left " #S "
+set -g status-left-length 20
+set -g status-right ""
+setw -g window-status-current-format " #I:#W "
+setw -g window-status-format " #I:#W "