Respect tmux clipboard policy and preserve empty reads

.github/workflows/test.yml

@@ -39,10 +39,11 @@ jobs:
             -w /workspace \
             archlinux:base-devel bash -lc '
               set -euo pipefail
-              pacman -Syu --noconfirm git jq neovim
+              pacman -Syu --noconfirm git jq neovim tmux python
               ./bin/sync-upstream self-test
               ./bin/sync-rebuilds --self-test
               ./bin/omarchy-pkgs self-test
               ./bin/omarchy-release self-test
               ./tests/neovim-remote-clipboard.sh
+              python tests/neovim-clipboard-tmux.py
             '