Brush Options: Tips shows each colorization method on a sample

Scatter, Art and Pattern Brush Options had no Tips button. The
reference app's Brushes page has one for Colorization, with information
and samples about each method.

A Tips button beside Method now opens Colorization Tips. For each
method it shows the name, what the method does, and a sample of the
brush as OK would make it, painted with that method on a blue stroke.
Hue Shift's sample uses the dialog's Key Color. A second click on Tips,
Escape or a click outside the popover closes it, and the dialog field
tips opens it from a command. Screen readers name the button, the
popover and each sample.

In every dialog, Escape with a dropdown list open now closes the list
and leaves the dialog open. Before, it canceled the dialog and
discarded its edits.

The stroke preview and the samples no longer panic when ui.dialog.set
writes a brush definition (__def) that is not a JSON object.

Docs: docs/target-app-parity.md.

docs/target-app-parity.md

@@ -723,6 +723,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   - **Brushes (part of #852):** double-clicking a brush in the Brushes panel (or the panel menu's Brush Options…) opens Calligraphic Brush Options (Name; Angle, Roundness and Size, each Fixed, Random or Pressure with its Variation; live previews of the nib and of a light–heavy–light stroke) or Bristle Brush Options (Shape and the bristle sliders); OK edits the brush and every stroke painted with it. The Paintbrush records the pen pressure along each stroke (kept with the path, saved, and joined when a stroke continues a path); a Calligraphic value on Pressure goes from value − variation at the lightest pressure to value + variation at the heaviest, on the canvas and in SVG, PDF and the other exports. Brushes saved before keep their look. Scatter Brush Options (Size, Spacing, Scatter and Rotation, each Fixed, Random between two values or Pressure from the first at the lightest pressure to the second at the heaviest; Rotation relative to Page or Path), Art Brush Options (Width, Scale Proportionately, Stretch to Fit Stroke Length or Stretch Between Guides with the guides' start and end, the four Directions, Flip Along and Across) and Pattern Brush Options (Scale, Spacing, the five tiles shown, Flip Along and Across, Stretch to fit, Add space to fit or Approximate path) each have Colorization (None, Tints, Tints and Shades, Hue Shift with its Key Color picked from the art's colours) and a live stroke preview; values from files and commands are clamped to their ranges. Still to come: the Art brush's Overlap, auto-generated Pattern brush corners, new tile art picked in Pattern Brush Options, Stylus Wheel, Tilt, Bearing and Rotation, and pen pressure on macOS.
     Type in a scatter brush's art takes the brush's colorization as its paths do: Tints, Tints and Shades and Hue Shift recolor the characters' solid fills and strokes in each copy the brush draws, and Brush Options' Key Color list, whose first color is Hue Shift's default key, counts the characters' fills and their strokes wider than 0. The Brushes page states that "The colors that a scatter, art, or pattern brush paints depend on the current stroke color and the colorization method of the brush" (<https://web.archive.org/web/20241230205225/https://helpx.adobe.com/illustrator/using/brushes.html>) and does not mention type there; recoloring the characters' paints like the art's fills and strokes is VectorCraft's own rule. The Symbol Stainer mixes the characters' strokes of type toward the stain as it mixes their fills. Evidence: `tests::scatter_colorization_recolors_type`, `tests::art_colors_list_the_most_used_first`, `tests::stain_mixes_type_strokes_too` (vectorcraft-brush).
     Art Brush Options' Width (1% to 1000%) and Pattern Brush Options' Scale (1% to 10000%) each have a slider beside the field, over the same range in whole percents; screen readers name the slider as its row and read the field's value.
+    Scatter, Art and Pattern Brush Options have the Tips button for Colorization that the [Brushes](https://web.archive.org/web/20241230205225/https://helpx.adobe.com/illustrator/using/brushes.html) page (archived copy) describes, beside Method. It opens Colorization Tips, which shows each method's name and what it does beside a sample of the brush, as OK would make it, painted with that method on a blue stroke; Hue Shift's sample uses the dialog's Key Color. `ui.dialog.set {field: "tips", value: true}` opens it. Screen readers name the button, the popover and each sample.
     Hue Shift set by `brush.new` or `brush.options` without a key color takes the color the art's fills and strokes use most, as Brush Options already offers it, following the Brushes page: "By default, the key color is the most prominent color in the art" (<https://web.archive.org/web/20241230205225/https://helpx.adobe.com/illustrator/using/brushes.html>). The page does not state how prominence is measured. Counting the fills and strokes that use each solid color, with the first one found winning a tie and black for art with no solid color, is VectorCraft's own rule. A `brush.options` edit that gives only the method keeps the brush's key color, and one that gives only an art brush's start guide keeps its end guide. Evidence: `tests_brushsym::hue_shift_without_a_key_takes_the_most_used_art_color`, `tests_brushsym::art_brush_options_keep_the_scale_fields_an_edit_leaves_out`.
     In the Brushes panel, Shift-click selects a range of brushes and Ctrl/Cmd-click adds or removes one. Delete Brush and Duplicate Brush then act on all of them (`brush.delete {names}`, `brush.duplicate {names}`).
     Document Info has a Brushes category after Graphic Styles. It lists the Brushes panel's brushes, or with Selection Only it lists the brushes that the selected objects' strokes use. The Document Info report and Package's report list them too (`document.info {category: "brushes"}`, `brushNames`).