Select Color: review cleanups

- Split ColorEditor::view into mode_row, slider_rows, field_view,
  hex_row and hex_field; output is unchanged.
- hex_string reuses config::rgb_to_hex, and parse_hex documents why it
  stays separate (it also accepts #RGB).
- ink_is_dark uses Color::into_rgba8 instead of rounding by hand.
- Remove four translation keys the old dialog used and nothing
  references any more, from the catalog and all 22 locales.
- Eyedropper: without a main window there is no screenshot to wait for,
  so leave the eyedropper; keep the magnifier inside small windows.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013rGmDUNr1hUf4zo1X3dak8

locales/ru-RU/opencadstudio.ftl

@@ -1325,8 +1325,6 @@ common =
     .dismiss = Закрыть
     .value-8a8de8 = ?
     .select-color-8dddf1 = { common.select-color }…
-    .no-recent-colors-yet = Недавно использованных цветов пока нет
-    .true-color-rgb = { common.true-color }    RGB __ocs_fmt_0__, __ocs_fmt_1__, __ocs_fmt_2__
     .index-color = { common.color } (ACI)
     .true-color = { common.color } (RGB)
     .standard-colors = { common.standard } · { common.color }
@@ -1334,9 +1332,7 @@ common =
     .nearest-index-color = Ближайший индекс
     .exact-index-match = Точное совпадение с индексом
     .cad-color-index-aci-10-249 = Индекс цвета ACI 10–249
-    .color-family-shade-intensity = { common.color-family } → · { common.shade } / { properties.intensity } ↓
     .grayscale-250-255 = { common.grayscale } 250–255
-    .recently-used = Недавно использованные
     .isometric-drafting = Изометрическое черчение
     .f5-cycles-the-active-plane = F5 циклически переключает активную плоскость.
     .units-5430a1 = { common.units }…