Fix bugs found in post-refactor audit

- verify-mvt.sh: remove dead first _info= line (used MVT_START before
  defined); fix JPEG size loop to accumulate bytes correctly and display
  human-readable total; show size in delete confirmation
- montage-mvt.sh: grep -c uses || echo 0 instead of || true to be
  unambiguous about the no-match value under set -e
- capture.sh, capture-watchdog.sh: require camera name arg, remove
  silent SUNRISE_CAM fallback
- migrate-seasons.sh: require --cam arg, error if missing
- README.md, sky-cam.conf: remove stale fullday-video.sh references;
  README pipeline diagram updated to show verify-mvt.sh

https://claude.ai/code/session_01C4jbd3waXG3eKZYbGUjLUQ

montage-mvt.sh

@@ -207,8 +207,8 @@ if ffmpeg -loglevel warning \
     actual_dur=$(ffprobe -v error -show_entries format=duration -of csv=p=0 "$output_file")
     dur_delta=$(echo "scale=1; $actual_dur - $music_duration" | bc | sed 's/^-//')
     stream_types=$(ffprobe -v error -show_entries stream=codec_type -of csv=p=0 "$output_file" 2>/dev/null)
-    has_video=$(echo "$stream_types" | grep -c "video" || true)
-    has_audio=$(echo "$stream_types" | grep -c "audio" || true)
+    has_video=$(echo "$stream_types" | grep -c "video" || echo 0)
+    has_audio=$(echo "$stream_types" | grep -c "audio" || echo 0)
     checks="duration=${actual_dur}s (drift ${dur_delta}s)"
     [ "$has_video" -gt 0 ] && checks="$checks  video=ok" || checks="$checks  video=MISSING"
     [ "$has_audio" -gt 0 ] && checks="$checks  audio=ok" || checks="$checks  audio=MISSING"