4-seasons: fix silent exit in grey-frame filter (read + set -e)

When SEASONS_GREY_STDDEV_MIN is enabled, ImageMagick's convert outputs
the stddev/mean values without a trailing newline.  read exits 1 on EOF-
without-newline even when it successfully populated the variables.  With
set -euo pipefail this kills the script silently on the very first image
that enters the grey-filter code path — producing the observed symptom:
script stops after "Images found:" with no error and no video.

Fix: append || true so read's EOF exit code is absorbed.  The variables
are still set correctly; only the exit code changes.

https://claude.ai/code/session_01U29A8NpgJ41tboiggZNmk8

4-seasons.sh

@@ -118,7 +118,7 @@ for img in "${all_images[@]}"; do
         if [ "$fsize" -lt "$LARGE_BYTES" ]; then
             read -r stddev mean < <(convert "$img" -colorspace Gray \
                 -format "%[fx:int(standard_deviation*255)] %[fx:int(mean*255)]" \
-                info: 2>/dev/null || echo "255 128")
+                info: 2>/dev/null || echo "255 128") || true
             if [ "${stddev:-255}" -lt "$GREY_MIN" ] && [ "${mean:-0}" -gt "$GREY_DARK_FLOOR" ]; then
                 ((grey++)) || true; continue
             fi