chore: format files with shfmt and resolve most shellcheck complaints

test/lib/runtime.test.sh

@@ -8,9 +8,11 @@ source "../test-helper.sh"
 source "${root}/lib/runtime.sh"
 
 # We assume env.sh has been sourced if $TMUXIFIER_LAYOUT_PATH has been set.
+# shellcheck disable=SC2016
 assert 'echo $TMUXIFIER_LAYOUT_PATH' "${TMUXIFIER}/layouts"
 
 # We ensure $session_root is set to $HOME by default.
+# shellcheck disable=SC2016
 assert 'echo $session_root' "$HOME"
 
 # We assume layout-helpers.sh has been sourced if a few of them are available.
@@ -18,6 +20,5 @@ for helper in new_window split_v split_h select_window select_pane; do
   assert "type $helper | head -1" "$helper is a function"
 done
 
-
 # End of tests.
 assert_end "runtime.sh"