treat Ctrl-D at the guess prompt like Enter

Ctrl-D doesn't move the cursor to a new line, but the retry prompts
move up a line assuming Enter was pressed, so each Ctrl-D climbed up
the screen over the keyboard and board. It also quit the game, losing
an offline game to a stray key press.

On a terminal, print the missing newline and carry on as if Enter was
pressed. Only exit when input has really ended (not a terminal), so a
closed pipe still can't spin the retry loop.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

wordle

@@ -247,16 +247,16 @@ function render_answer() {
   echo -en "${NEWLINE}${RESET}"
 }
 
-# Exits non-zero at end of input (Ctrl-D) so the caller can quit
+# Exits non-zero when input has ended so the caller can quit
 function retrieve_guess() {
   if  [[ -n $1 ]]; then
-    read -r -p "${CLEAR_UP1}$1: " GUESS || exit 1
+    read -r -p "${CLEAR_UP1}$1: " GUESS || end_of_input
   else
-    read -r -p "${CLEAR_2END}Enter Guess: " GUESS || exit 1
+    read -r -p "${CLEAR_2END}Enter Guess: " GUESS || end_of_input
   fi
 
   while [[ ${#GUESS} -ne 5 ]] || [[ ! "${GUESS,,}" =~ ^[a-z]{5}$ ]]; do
-    read -r -p "${CLEAR_UP1}Must be 5 letters: " GUESS || exit 1
+    read -r -p "${CLEAR_UP1}Must be 5 letters: " GUESS || end_of_input
   done
   declare valid_guess
   validate_guess "${GUESS}" ; valid_guess=$?
@@ -278,6 +278,14 @@ function retrieve_guess() {
   echo -n "${GUESS^^}"
 }
 
+# Called when read gets Ctrl-D. On a terminal treat it like Enter, but if
+# input has really ended (closed pipe) exit, or the retry loop spins forever
+function end_of_input() {
+  [[ -t 0 ]] || exit 1
+  # Ctrl-D doesn't move to a new line like Enter, which the prompts expect
+  echo -en "${NEWLINE}" >&2
+}
+
 function render_keyboard() {
   declare pos=$(( BORDER*2+7 ))
   echo -en "${RESET}\e[$pos;0H"