bread-theme: add libadwaita components + fix slider/chip theming gaps

New `adw` feature (gated separately from `gtk`, since AdwApplicationWindow
isn't compatible with gtk4-layer-shell — the five panel/launcher apps stay
on plain `gtk`, only breadman/breadhelp-style plain-window apps want this):
preferences_group/toggle_row/spin_row/action_row/preferences_page, wrapping
libadwaita's PreferencesGroup/SwitchRow/SpinRow/ActionRow/PreferencesPage.
adw::init() also forces dark color-scheme, since bread-theme's whole design
is a fixed dark base regardless of system GTK preference.

These directly target defects a design critique found: hand-rolled
switch+label rows with no intrinsic width (breadman/settings' ~1400px
stretched toggles) and spinners stranded far from their label — both just
don't happen when the row is a real AdwSwitchRow/AdwSpinRow instead of a
box assembled from scratch.

Also, two shared-stylesheet fixes usable by every app immediately, gtk
feature only:
- `scale` (slider) had no rule at all, so every volume/brightness slider
  showed GTK's own default blue instead of the palette accent — the same
  critique flagged breadbar's control-panel sliders contradicting its own
  on-brand OSD fill two clicks away.
- A new `chip()`/`set_chip_active()` helper in gtk.rs uses the existing
  (already-tokenized, already-defined) `.chip`/`.pill` stylesheet rule
  instead of each app hand-rolling its own filter-chip CSS — which is how
  breadclip/breadpad/breadman ended up with three different, mutually
  disagreeing pill fills for what's supposed to be one shared component.

bread-theme/src/adw.rs

@@ -0,0 +1,78 @@
+//! Composite libadwaita widgets for the bread ecosystem's design system —
+//! the actual mechanism (real GNOME-style widgets, not more hand-rolled CSS)
+//! behind why bos-settings' sidebar/section/toggle rows read as more polished
+//! than the plain-GTK4 apps'. An app calls these instead of assembling boxes
+//! and labels and raw widgets from scratch each time, so spacing/sizing/
+//! grouping decisions get made once, correctly, here — not re-derived per
+//! screen.
+//!
+//! Not usable from the five `gtk4-layer-shell` apps (breadbar, breadbox,
+//! breadclip, breadsearch, breadpad): `AdwApplicationWindow`'s own chrome
+//! isn't compatible with a layer-shell surface, and these helpers assume an
+//! ordinary top-level window. Apps with a plain top-level window (breadman,
+//! breadhelp) can use the full set.
+
+use libadwaita as adw;
+use adw::prelude::*;
+
+/// Call once at startup, before building any widgets from this module —
+/// initializes libadwaita's style manager and forces dark mode regardless of
+/// the system GTK theme preference. bread-theme's whole design is a *fixed*
+/// dark base (only the accent tracks pywal — see `palette::FIXED_BACKGROUND`
+/// etc.) so an app respecting a light system preference here would silently
+/// break that contract the moment someone's GNOME settings say "light".
+pub fn init() {
+    adw::init().expect("failed to initialize libadwaita");
+    adw::StyleManager::default().set_color_scheme(adw::ColorScheme::ForceDark);
+}
+
+/// A titled, optionally-described group of setting rows — the
+/// title-then-description-then-rows rhythm bos-settings already uses per
+/// section, now available to native GTK4/relm4 apps instead of a hand-rolled
+/// vbox with a bold label glued to the top.
+pub fn preferences_group(title: &str, description: Option<&str>) -> adw::PreferencesGroup {
+    let group = adw::PreferencesGroup::builder().title(title).build();
+    if let Some(desc) = description {
+        group.set_description(Some(desc));
+    }
+    group
+}
+
+/// A single on/off setting row with a correctly-sized, correctly-positioned
+/// switch — the direct fix for the ~1400px-wide stretched-switch bug
+/// (breadman/settings had no intrinsic width on its hand-rolled switch, so
+/// it filled the row like a progress bar).
+pub fn toggle_row(title: &str, subtitle: Option<&str>, active: bool) -> adw::SwitchRow {
+    let row = adw::SwitchRow::builder().title(title).active(active).build();
+    if let Some(sub) = subtitle {
+        row.set_subtitle(sub);
+    }
+    row
+}
+
+/// A single numeric setting row (spin button docked to its own label,
+/// instead of stranded ~1300px away at the window's far edge).
+pub fn spin_row(title: &str, subtitle: Option<&str>, adjustment: &gtk4::Adjustment) -> adw::SpinRow {
+    let row = adw::SpinRow::builder().title(title).adjustment(adjustment).build();
+    if let Some(sub) = subtitle {
+        row.set_subtitle(sub);
+    }
+    row
+}
+
+/// A general label(+subtitle) row with room for a trailing widget
+/// (`row.add_suffix(&widget)`) — for settings that don't fit switch/spin
+/// (text entries, buttons, dropdowns, a raw value display).
+pub fn action_row(title: &str, subtitle: Option<&str>) -> adw::ActionRow {
+    let row = adw::ActionRow::builder().title(title).build();
+    if let Some(sub) = subtitle {
+        row.set_subtitle(sub);
+    }
+    row
+}
+
+/// A page of one or more `preferences_group`s, with correct margins and
+/// scroll handling — the top-level content container for a settings screen.
+pub fn preferences_page() -> adw::PreferencesPage {
+    adw::PreferencesPage::new()
+}

bread-theme/src/gtk.rs

@@ -114,6 +114,29 @@ pub fn apply_css(css: &str, provider: &RefCell<Option<CssProvider>>) {
     }
 }
 
+/// A filter/tag chip using the shared `.chip` stylesheet rule (an
+/// `@overlay`-filled pill, `@accent`-filled when the `active` CSS class is
+/// set) instead of a fresh literal color — this is the fix for the same
+/// component drifting to three different fills across breadclip (grey),
+/// breadpad, and breadman (both cream), none of which agreed with each
+/// other or with the shared token.
+pub fn chip(label: &str) -> gtk4::Button {
+    gtk4::Button::builder().label(label).css_classes(["chip"]).build()
+}
+
+/// Toggles a chip's (or any widget's) `active` CSS class — the `.chip.active`
+/// stylesheet rule fills it with the accent instead of the neutral overlay.
+/// Wiring *when* a chip becomes active (single-select filter, multi-select
+/// tags, etc.) is genuinely per-app, so that stays the caller's job; this is
+/// just the one-line visual toggle every case needs.
+pub fn set_chip_active(chip: &impl IsA<gtk4::Widget>, active: bool) {
+    if active {
+        chip.add_css_class("active");
+    } else {
+        chip.remove_css_class("active");
+    }
+}
+
 /// Apply a user CSS override file at USER priority. Clears the provider if the
 /// file is absent so stale overrides don't persist across SIGHUP reloads.
 pub fn apply_user_css(path: &Path, provider: &RefCell<Option<CssProvider>>) {

bread-theme/src/lib.rs

@@ -1,6 +1,8 @@
 pub mod palette;
 #[cfg(feature = "gtk")]
 pub mod gtk;
+#[cfg(feature = "adw")]
+pub mod adw;
 
 pub use palette::{load_palette, Palette};
 
@@ -187,6 +189,14 @@ pub fn stylesheet(p: &Palette) -> String {
          switch {{ background-color: @overlay; border-radius: {pill}px; }}\n\
          switch:checked {{ background-color: @accent; }}\n\
          switch slider {{ background-color: @on-surface; border-radius: {pill}px; }}\n\
+         /* GtkScale (sliders) render with GTK's own default accent (a fixed\
+            blue, independent of the app's theme) unless styled explicitly —\
+            every app with a volume/brightness slider was silently showing\
+            that default instead of the palette's accent until this rule\
+            existed. */\n\
+         scale trough {{ background-color: @overlay; border-radius: {pill}px; min-height: 6px; }}\n\
+         scale trough highlight {{ background-color: @accent; border-radius: {pill}px; min-height: 6px; }}\n\
+         scale slider {{ background-color: @on-bg; border-radius: {pill}px; }}\n\
          list, listbox {{ background-color: transparent; }}\n\
          row {{ border-radius: {r2}px; }}\n\
          row:selected, list row:selected {{ background-color: @accent; color: @on-accent; }}\n\