The user found too much unexplained: what "50% [ , ] 90% [ , ]" means,
and many other numbers and words of the screens.

- helptext.py: 35 topics in plain Russian, by sections, from the
  fraction, the median and the intervals to the levels, ESS, log Z,
  the checks, each figure and the joint report. Their numbers are those
  of the code: ESS 30 and 100, Δ log Z 5 nats, 5% of the weight below
  0.2 or at 90% of the cap, a settled estimate within 0.005 at ESS 100.
- widgets.HelpButton: a «?» next to a card, a figure or a group of
  settings, with a short tooltip; a click opens the topic in a popup,
  whose link opens it on «Справка».
- help_screen.py: «Справка», the fifth item of the navigation, has every
  topic on one page after their contents; F1 opens it at the topic of
  the screen shown.
- Tooltips for the columns of both tables, the numbers of the estimate
  and of the joint report, the views and the layers of the model, the
  tabs of «Результаты», and the fields that had none (wide peaks,
  threads). Tooltips are rich text now (widgets.tooltip), which Qt
  wraps; plain text stayed one line, however long.
- The intervals read "с вероятностью 50% — от … до …, 90% — от … до …",
  and the column «Доля [25%, 75%]» is «Доля [50% интервал]».
- The tooltip of the region of the wide peaks said it was orange; it is
  the light blue band at the bottom of the plot.
- The self-test takes a screenshot of «Справка».

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