                        Changes in version 0.4.0                        

Breaking: sleep_annotation() needs a sleep rule. To reproduce earlier
results, add rule = "classic", or declare it once with
options(sleepr.sleep_rule = "classic") (or SLEEPR_SLEEP_RULE=classic in
.Renviron). With scopr, extra arguments reach FUN:
load_ethoscope(metadata, FUN = sleep_annotation, rule = "classic").
Without a rule, sleep_annotation() stops with an explanation.

  - rule = "k" (k = 3 by default; "k2" is stricter): sleep scored from
    walking and sustained movement events, ignoring tracking noise. It
    matches video ground truth at night, and flies it scores asleep
    respond to air puffs like sleeping flies. The algorithm and defaults
    are identical to ethoscopy 3.0.0 (sleep_rules).
  - untracked = "immobile" (default, as before) or "break" in
    sleep_annotation().
  - motion_qc(): per animal and light phase, how often a still animal
    crosses the classic threshold, and how much of the recording is
    untracked; with the helpers find_still_bins(), find_spikes(),
    light_phase(), pixel_size() and default_still_shift().
  - classify_events() and k_rule_bins() are exported.
