Add a fake header row and size the checklist width to the terminal

Header row: a first, non-functional checklist entry using the exact same
printf field widths as the real rows ("x #  NAME" / "x 1  caddy" / ...),
so it visually reads as column headers for the x/# prefix even though
whiptail has no real header concept. Its sentinel tag ("NAME") is filtered
back out of the selection after the dialog closes, so it's harmless even
if someone checks it and hits <Ok>.

Width: was a flat 78 regardless of the actual terminal, so descriptions
got cut off mid-sentence on anything wider with no way to read the rest
(confirmed from a screenshot — "TURN via the shared coturn s..." trailing
off). Scale with tput cols instead, floored at the old 78 (safe on a plain
80-column terminal) and capped at 160 so a very wide terminal doesn't get
an absurdly wide dialog.

setup.sh

@@ -414,13 +414,23 @@ while true; do
         # for a non-terminal/unknown size) so this can't request a dialog
         # taller than the screen.
         _term_lines="$(tput lines 2>/dev/null </dev/tty || echo 24)"
-        _list_h=${#SVCS[@]}
-        [ "$_list_h" -gt 20 ] && _list_h=20
+        _term_cols="$(tput cols 2>/dev/null </dev/tty || echo 80)"
+        # +1 list row for the fake header row added below.
+        _list_h=$((${#SVCS[@]} + 1))
+        [ "$_list_h" -gt 21 ] && _list_h=21
         _term_cap=$((_term_lines - 10))
         [ "$_term_cap" -lt 6 ] && _term_cap=6
         [ "$_list_h" -gt "$_term_cap" ] && _list_h="$_term_cap"
         _box_h=$((_list_h + 8))
         [ "$_box_h" -gt "$((_term_lines - 2))" ] && _box_h=$((_term_lines - 2))
+        # Was a flat 78 regardless of actual terminal size — descriptions
+        # got cut off mid-sentence on any terminal wider than that, with no
+        # way to read the rest. Scale with the terminal instead, floored at
+        # the old 78 (safe on a plain 80-column default) and capped so a
+        # very wide terminal doesn't get an absurdly wide dialog.
+        _box_w=$((_term_cols - 4))
+        [ "$_box_w" -lt 78 ] && _box_w=78
+        [ "$_box_w" -gt 160 ] && _box_w=160
 
         # whiptail's checklist has exactly one interactive element per row —
         # the checkbox itself. The "tag" field (what's displayed right after
@@ -433,6 +443,13 @@ while true; do
         # width, but it's still one string under the hood. Extracted back
         # into just the plain service name below before dispatch.
         svc_items=()
+        # Fake header row, first in the list, using the exact same field
+        # widths as the real rows below so "x"/"#"/name visually line up as
+        # columns. Its tag's last token ("NAME") is a sentinel filtered back
+        # out after selection — toggling it is harmless either way (nothing
+        # is registered under that name), but this keeps <Ok> silently
+        # correct even if someone does check it out of habit.
+        svc_items+=("$(printf "%s %s %s" "x" "$(printf '%-2s' '#')" "NAME")" "── service ──" "OFF")
         for name in "${SVCS[@]}"; do
             _inst_mark=" "
             _count_str="  "
@@ -445,12 +462,15 @@ while true; do
             svc_items+=("$svc_tag" "${SERVICE_DESC[$name]}" "OFF")
         done
         CHOICE=$(whiptail --title "${CHOSEN_CAT^^}" --checklist \
-            "installed(x) #instances  name                    Space=select to install, Enter=go:" "$_box_h" 78 "$_list_h" \
+            "Space=select to install, Enter=go. Top row shows the x/# column meaning:" "$_box_h" "$_box_w" "$_list_h" \
             "${svc_items[@]}" 3>&1 1>&2 2>&3 </dev/tty) || continue
         eval "SELECTED=($CHOICE)"
         # Undo the display-only "x N " prefix — name is always the last
         # whitespace-separated token, since service names never contain spaces.
         for i in "${!SELECTED[@]}"; do SELECTED[$i]="${SELECTED[$i]##* }"; done
+        _filtered=()
+        for _s in "${SELECTED[@]}"; do [ "$_s" != "NAME" ] && _filtered+=("$_s"); done
+        SELECTED=("${_filtered[@]}")
     else
         echo ""; echo "${CHOSEN_CAT^^}:"
         for name in "${SVCS[@]}"; do