Fix ShellCheck warnings and update CI lint rules

sourcedialog: remove unused ck/scb variables, move SC2206/SC2034
directives to correct lines, split local+assign for scroll_color.
CI: exclude SC1091/SC2034/SC2154 for examples/tutorials (false
positives from dynamic library variables).

Author: robin

.github/workflows/tests.yml

@@ -51,4 +51,4 @@ jobs:
       - name: Install shellcheck
         run: sudo apt-get update && sudo apt-get install -y shellcheck
       - name: Run shellcheck on examples
-        run: shellcheck -s bash examples/* tutorial/*
+        run: shellcheck -s bash --exclude=SC1091,SC2034,SC2154 examples/* tutorial/*

sourcedialog

@@ -824,7 +824,8 @@ _sd_listbox_draw() {
     [[ $mark == no ]] || (( x += _SD_MARK_WIDTH ))
     (( ilight - ifirst < height )) && _sd_pos "$(( y + ilight - ifirst ))" "$x"
 
-    local scroll_color="$sgr0$(_sd_fg "$_SD_LIST_FG")$(_sd_bg "$_SD_LIST_BG")"
+    local scroll_color
+    scroll_color="$sgr0$(_sd_fg "$_SD_LIST_FG")$(_sd_bg "$_SD_LIST_BG")"
     if (( ifirst > 0 )); then
         _sd_pos "$y" "$(( x + width - 1 ))"
         printf '%s' "${scroll_color}$_SD_SCROLL_UP"