Add Arch Wayland dotfiles: sway/waybar/kitty/nvim/zsh, idempotent installer

Auto-adapts sway workspace routing to however many monitors are
connected (laptop vs. desktop) instead of hardcoding output names.

config/sway/conf.d/10-appearance.conf

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+font pango:JetBrainsMono Nerd Font 10
+gaps inner 8
+gaps outer 4
+default_border pixel 2
+default_floating_border pixel 2
+
+client.focused          #3b82f6 #000000 #60a5fa #2563eb #3b82f6
+client.focused_inactive #171717 #000000 #737373 #171717 #171717
+client.unfocused        #0a0a0a #000000 #525252 #0a0a0a #0a0a0a
+client.urgent           #60a5fa #000000 #60a5fa #3b82f6 #60a5fa
+
+for_window [app_id="system-monitor"] floating enable, resize set 1000 700, move position center
+
+output * bg ~/.config/sway/wallpapers/blue-horizon.svg fill
+
+# Desktop-only dual-monitor arrangement: DP-3 is the centered primary
+# display, DP-2 sits immediately to its left. Sway silently ignores
+# `output` directives for names that don't exist, so this is a no-op on
+# the single-monitor laptop (its internal panel, e.g. eDP-1, is untouched
+# and simply gets everything). Workspace-to-output routing is not pinned
+# here; scripts/select-workspace.sh assigns workspaces to whichever
+# outputs are actually connected, in left-to-right order, so it adapts
+# automatically on both machines without any per-host config.
+output DP-3 position 0 0
+output DP-2 position -2560 0
+
+output DP-3 scale 1
+output DP-2 scale 1

config/sway/conf.d/20-input.conf

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+input type:keyboard {
+    xkb_layout us
+    repeat_delay 300
+    repeat_rate 40
+}
+
+input type:touchpad {
+    tap enabled
+    natural_scroll enabled
+    dwt enabled
+}
+
+# Make workspace number bindings follow the monitor under the pointer.
+focus_follows_mouse always

config/sway/conf.d/40-autostart.conf

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+exec_always --no-startup-id sh -c 'pkill waybar; exec waybar'
+exec --no-startup-id mako
+exec --no-startup-id nm-applet --indicator
+exec --no-startup-id /usr/lib/polkit-gnome/polkit-gnome-authentication-agent-1