Hide the phantom empty top bar, keep only the Gin sidebar

Core Navigation's top bar only shows itself when its tools/context/
actions regions are non-empty (`:has(:not(:empty))`). With no blocks
placed in those regions, they still contain whitespace text nodes from
Twig's loop scaffolding, which defeats that check -- the bar rendered
anyway, empty, and pushed page content down to make room for it.

Attached globally via hook_page_attachments() rather than scoped to
/lignes or /dashboard, since the Navigation chrome renders on every
authenticated page, not just our custom routes.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/modules/custom/figli_compta_ledger/css/admin-chrome.css

@@ -0,0 +1,14 @@
+/* Core Navigation's top bar (`.top-bar`) only shows itself when its
+   tools/context/actions regions are non-empty -- but with no blocks placed
+   there, the regions still contain whitespace text nodes from the Twig
+   loop scaffolding, which defeats the `:not(:empty)` check. Result: an
+   empty top bar renders anyway, with the page content pushed down to make
+   room for it. We only use the Gin sidebar (the left icon rail), so force
+   the phantom bar off and collapse the space it would otherwise reserve. */
+.top-bar {
+  display: none !important;
+}
+
+.top-bar ~ .dialog-off-canvas-main-canvas {
+  margin-block-start: 0 !important;
+}