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.lock

@@ -150,13 +150,22 @@ version = "2.13.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b588b76d00fde79687d7646a9b5bdf3cc0f655e0bbd080335a95d7e96f3587da"
 
+[[package]]
+name = "bread-launcher"
+version = "0.7.4"
+dependencies = [
+ "bread-utils 0.7.4",
+ "gtk4",
+ "serde_json",
+]
+
 [[package]]
 name = "bread-screenshots"
 version = "0.7.4"
 source = "git+https://git.breadway.dev/Breadway/bread-ecosystem?tag=v0.7.4#a9754d90ed32efcc26765abd01c9f441bfb01b1e"
 dependencies = [
  "anyhow",
- "bread-utils",
+ "bread-utils 0.7.4 (git+https://git.breadway.dev/Breadway/bread-ecosystem?tag=v0.7.4)",
  "tracing",
 ]
 
@@ -196,6 +205,16 @@ dependencies = [
  "tracing",
 ]
 
+[[package]]
+name = "bread-utils"
+version = "0.7.4"
+dependencies = [
+ "bread-shared 0.7.0",
+ "dirs 5.0.1",
+ "serde",
+ "serde_json",
+]
+
 [[package]]
 name = "bread-utils"
 version = "0.7.4"
@@ -212,10 +231,11 @@ name = "breadbar"
 version = "0.3.3"
 dependencies = [
  "anyhow",
+ "bread-launcher",
  "bread-screenshots",
  "bread-shared 0.8.0",
  "bread-theme",
- "bread-utils",
+ "bread-utils 0.7.4 (git+https://git.breadway.dev/Breadway/bread-ecosystem?tag=v0.7.4)",
  "clap",
  "futures-lite",
  "gtk4",