Settings: a settings window, its sections, a search, and what fills them

SettingsLayout lists sections down the side and shows the open one, the
list going above the page in a narrow box; SettingsSection and
SettingsRow title and hold settings, a row's control wrapping under its
name. SettingsSearch finds a setting by its name or words and opens its
section. ThemeSelector, AccentColorPicker, FontSizeControl and
DensitySelector set the look; KeyboardShortcutsList finds shortcuts by
every word; ProxySettings, PrivacySettings, NotificationSettings,
StartupSettings, StorageSettings with its clear, ImportExportSettings,
ResetToDefault, FeatureFlags and DeveloperModeToggle fill the rest.
Every handler a control needs is required and fails loud when missing.
ColorPalette wraps its swatches in a row capped at its columns, so it
keeps their size in a box sized by its content, and its swatches carry
the palette's id. ThemeSwitcher points here: src/theme sits under the
chapters that draw with buttons.

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

examples/gallery/pages/mod.rs

@@ -28,6 +28,7 @@ mod navigation;
 mod overlays;
 mod primitives;
 mod project;
+mod settings;
 mod shell;
 mod tables;
 mod terminal;
@@ -83,6 +84,7 @@ pub const ALL: &[Page] = &[
     canvas::PAGE,
     devtools::PAGE,
     dashboard::PAGE,
+    settings::PAGE,
     theme::PAGE,
 ];