feat(yahweh-launcher): F3 — extracción del shell standard de explorers

Iter 19. Patrón con 4 consumers idénticos: cada main() repetía el mismo
~20 líneas de boot (Application::new + Theme::install_default +
cx.open_window + WindowOptions + cx.activate). Sólo varían título,
tamaño y root factory.

crates/modules/ui_engine/libs/launcher/:
- pub fn launch_app(title, size, root_factory) → 1-line boot.
- pub fn launch_app_with(config, root_factory) → variante con config
  armado afuera (env-var driven, etc).
- pub struct AppLaunchConfig::new(title, size).
- 2 tests cubren normalización del config.

Migración 4 consumers (nakui/nouser/minga/brahman-broker explorer):
- main() pasa de ~20 líneas a 1: launch_app(...).
- Imports gpui podados (no más App/Application/Bounds/WindowOpts/etc).
- Cada uno agrega dep yahweh-launcher.

Naming: yahweh-shell ya existe (bootstrap heavyweight con file/db/text
viewers en crates/apps/). Helper liviano queda como yahweh-launcher.

Ahorro ~75 líneas de boot hardcoded. Cambios de window/theme boot
ahora en un solo lugar.

2/2 tests launcher; 4 consumer suites intactas, todo verde.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/apps/brahman-broker-explorer/src/main.rs

@@ -29,35 +29,19 @@ use std::time::{Duration, Instant};
 use brahman_handshake::transport;
 use brahman_sidecar::{await_provider_blocking, build_consumer_card, ConsumerError};
 use gpui::{
-    div, prelude::*, px, App, Application, Bounds, Context, IntoElement, Render, SharedString,
-    Window, WindowBounds, WindowOptions,
+    div, prelude::*, px, Context, IntoElement, Render, SharedString, Window,
 };
+use yahweh_launcher::launch_app;
 use yahweh_theme::Theme;
+use yahweh_widget_app_header::app_header;
 use yahweh_widget_banner::{banner_themed, Banner};
 use yahweh_widget_stat_card::stat_card;
-use yahweh_widget_app_header::app_header;
 
 const POLL_INTERVAL: Duration = Duration::from_secs(5);
 const PROBE_TIMEOUT: Duration = Duration::from_secs(1);
 
 fn main() {
-    Application::new().run(|cx: &mut App| {
-        Theme::install_default(cx);
-        let bounds = Bounds::centered(None, gpui::size(px(720.), px(480.)), cx);
-        cx.open_window(
-            WindowOptions {
-                window_bounds: Some(WindowBounds::Windowed(bounds)),
-                titlebar: Some(gpui::TitlebarOptions {
-                    title: Some(SharedString::from("Brahman Broker — Probe")),
-                    ..Default::default()
-                }),
-                ..Default::default()
-            },
-            |_w, cx| cx.new(Explorer::new),
-        )
-        .expect("open window");
-        cx.activate(true);
-    });
+    launch_app("Brahman Broker — Probe", (720., 480.), Explorer::new);
 }
 
 /// Snapshot de un probe.