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

sky-cam.conf

@@ -21,9 +21,8 @@
 #
 #   systemctl --user daemon-reload
 #   systemctl --user enable --now sky-cam-sunrise.timer
-#   systemctl --user enable --now sky-cam-seasons-sunrise.timer
-#   systemctl --user enable --now sky-cam-fullday-sunrise.timer
-#   # one sky-cam-seasons-<cam>.timer and sky-cam-fullday-<cam>.timer per camera
+#   # one sky-cam-seasons-<cam>.timer per camera, e.g.:
+#   systemctl --user enable --now sky-cam-seasons-east.timer
 #
 # Check status:
 #   systemctl --user list-timers 'sky-cam-*'