T25a Generative: prompt and settings

PromptEnhancer offers a fuller prompt with the words it adds washed,
split at punctuation; Use this takes it into the field, Keep mine
lets it go. StylePresetPicker and AspectRatioPicker are rows of Tab
stops, the chosen one in accent; a ratio chip draws its shape.
SeedInput keeps digits up to u32::MAX and rolls one with a die.
NegativePromptInput and ImageGenerationPanel point to forms::TagInput
and forms::Form. theme.generative() holds the chapter's sizes. The
gallery's preset pictures are the atrium photo in five styles.

src/primitives/icon.rs

@@ -56,6 +56,7 @@ icons! {
     ArrowUpRight => "arrow-up-right",
     ArrowUp => "arrow-up",
     AtSign => "at-sign",
+    Ban => "ban",
     Battery => "battery",
     Bell => "bell",
     Bold => "bold",
@@ -115,6 +116,7 @@ icons! {
     Crop => "crop",
     Crosshair => "crosshair",
     Database => "database",
+    Dices => "dices",
     DollarSign => "dollar-sign",
     Dot => "dot",
     Download => "download",