bar: implement spotlight's embedded launcher capsule (Phase 6b)

- New bread-launcher dep (gtk feature), pinned tag v0.7.4 with a dev-only
  [patch] entry alongside bread-theme's.
- Wire the drawer slot (plan §2/§7): root becomes a vbox whose first row is
  the existing CenterBox and whose second is drawer_box, appended via the
  same ModuleRegistry::for_each_in_slot pattern left/centre/right already
  use. Empty for liquid-motion/glass-workbench (zero children, zero size);
  theme.rs's window.breadbar > centerbox selector becomes > box > centerbox
  to follow the new nesting, byte-identical CSS for both existing themes.
- modules.workspaces.style = dots: bar::workspaces::make_dot_button, width
  from modules.workspaces.dot_widths, wired as a third rebuild_buttons arm.
- New launcher_entry (plain GtkEntry) and launcher_results
  (bread_launcher::gtk::ResultsList, sharing breadbox's cache/history via
  bread_launcher::LAUNCHER_APP) modules, built unconditionally and placed
  only when a theme's [bar.slots] names them (spotlight today).
- Capsule expand/collapse: typing/focus opens the drawer and animates its
  height via bread_theme::anim::spring_to; Up/Down move the selection,
  Enter launches (do_launch + record_launch) and collapses, Escape collapses
  and releases keyboard focus (on_demand ties to GTK's own focus-widget
  state, so releasing GTK focus hands the compositor keyboard back).
- window.width now wires Width::Px into set_default_width (previously
  unconsumed — Fill-anchored themes never needed it, the capsule does).
- Two new --screenshot views: capsule-collapsed, capsule-expanded (the
  latter focuses launcher_entry, types a query, and captures bar height +
  the drawer's actual settled height rather than a guessed constant).

cargo check/clippy: no new warnings (same two pre-existing: dead_code on
system_stats_box/cpu_pair/mem_pair/pwr_pair, from_* on workspaces.rs).
cargo test: 18/18 unchanged.

Cargo.toml

@@ -21,6 +21,11 @@ bread-utils = { git = "https://git.breadway.dev/Breadway/bread-ecosystem", tag =
 bread-shared = { git = "https://git.breadway.dev/Breadway/bread", tag = "v0.8.0-rc.1" }
 # Capture primitives for `--screenshot` mode — see src/screenshot.rs.
 bread-screenshots = { git = "https://git.breadway.dev/Breadway/bread-ecosystem", tag = "v0.7.4" }
+# Headless app-launcher core + GTK4 results-list widget (plan §3/§7): theme
+# 04/spotlight embeds the SAME `ResultsList` breadbox's overlay wraps, via
+# `bar::launcher_results` — one implementation, two hosts. `gtk` feature for
+# the results widget itself.
+bread-launcher = { git = "https://git.breadway.dev/Breadway/bread-ecosystem", tag = "v0.7.4", features = ["gtk"] }
 gtk4 = { version = "0.11", features = ["v4_12"] }
 gtk4-layer-shell = "0.8"
 relm4 = { version = "0.11", features = ["macros"] }
@@ -46,3 +51,4 @@ strip = "symbols"
 # (feature/shell-theme-manifest) before it is tagged as a release.
 [patch."https://git.breadway.dev/Breadway/bread-ecosystem"]
 bread-theme = { path = "../bread-ecosystem/bread-theme" }
+bread-launcher = { path = "../bread-ecosystem/bread-launcher" }