v0.22.2

Patch: decorative layers, fill value formatter, refline tooltips,
annotation ink, boxplot identity mapping.

Added

• GGPlot::decorative() marks the most recently added layer as purely
  decorative (#161): its drawn marks keep their own visual style but carry
  no per-mark metadata — no <title>, no data-x/data-series/
  data-value/data-fvalue, and no data_attr attributes — so an SVG
  consumer that treats "has a non-empty <title>" as "is a selectable
  data point" doesn't pick it up (e.g. a boxplot's own mean dot, drawn by
  a separate geom_point layer purely to mark the spot). Implemented as a
  private delegating Geom wrapper rather than a new Layer field, so it
  adds no field to any public struct. A .tooltip(...) on a decorative
  layer has no visible effect and warns, like the existing has-no-effect
  warning. A decorative layer also defaults to hidden in the legend,
  unless show_legend(true) is called to opt back in. Its marks are tagged
  data-part="decorative" and aria-hidden="true" (keeping data-geom),
  and their class is gg-mark gg-decorative instead of the geom's own
  (gg-point, gg-line, …), so a stylesheet selecting on the geom class
  doesn't restyle them as data marks.
• with_value_formatter (same signature as
  ScaleContinuous::with_value_formatter) on every continuous colour/fill
  scale that implements format_value: ScaleColorContinuous,
  ScaleColorGradientN and ScaleColorGradient2 (#164). Falls back to
  the plain locale-formatted number when unset (byte-identical default
  output).

Fixed

• geom_hline/geom_vline/geom_abline now implement Geom:: consumes_tooltips and read a layer's tooltip() template (e.g.
  .tooltip("{xintercept}")), replacing their own default "x = …"/
  "y = …" label the same way every other consumes_tooltips geom does;
  previously the template was silently dropped with a has-no-effect
  warning (#165). The default label (no template set) is unchanged.
  A mapped reference line's data_attr attributes no longer carry over
  onto the marks drawn after it (annotations, gridlines drawn on top,
  legend keys).
• annotate_text/annotate_segment now follow theme element_geom ink
  when their colour is still at its hard-coded default, the same as every
  other geom's default colour (#157, follow-up to #142) — previously they
  stayed near-black and nearly invisible under a white-on-black theme.
  annotate_rect's fill is deliberately excluded, matching ggplot2
  4.0.3's own behaviour (checked directly: its fill stays the hard-coded
  grey under element_geom(ink=, paper=) too). Default theme (no ink set)
  is byte-identical.
• geom_boxplot(stat = "identity"): a raw, unmapped ymin/ymax column
  no longer satisfies the five-number-summary requirement, matching
  ggplot2 4.0.3 (checked directly) and the same "only when actually
  mapped" treatment lower/middle/upper/outliers already got (#160,
  follow-up to #158). Scoped to GeomBoxplot alone; the universal raw-y
  convention for other geoms is unchanged.