Split pane chrome out of splits.rs into chrome::split_pane

splits.rs had grown to 551 lines after adding the design's pane header.
Move the header renderer, the close glyph, the URL helpers, and the
compact-canvas placeholder into chrome::split_pane so splits.rs is back
to a 422-line action + render orchestrator and the new helpers stay
under their own 150-line file.

Behaviour preserved: the pane click still selects the tab, the close
glyph still selects+closes, and pane_host/path/secure still derive from
the same UrlText fields.

crates/ely_app/src/shell/chrome/mod.rs

@@ -3,6 +3,7 @@ pub(crate) mod home;
 pub(crate) mod settings_layout;
 pub(crate) mod sidebar;
 pub(crate) mod sidebar_header;
+pub(crate) mod split_pane;
 pub(crate) mod topbar;
 pub(crate) mod wallpaper;
 
@@ -11,5 +12,9 @@ pub(crate) use home::render_home_page;
 pub(crate) use settings_layout::render_settings_landing;
 pub(crate) use sidebar::{PANEL_BG, panel_shadow};
 pub(crate) use sidebar_header::render_sidebar_header;
+pub(crate) use split_pane::{
+    pane_host_label, pane_path_label, pane_url_is_secure, render_compact_split_canvas,
+    render_split_pane_header,
+};
 pub(crate) use topbar::render_topbar;
 pub(crate) use wallpaper::{WallpaperTheme, render_wallpaper};