ui: draw the sidebar tabs without the placeholder icon

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/ui_app.hpp

@@ -444,6 +444,9 @@ struct App {
   /// are words (`wide` policy, a title per page), so the label count must equal the page count.
   int dbg_switcher_pills = -1;
   int dbg_switcher_labels = -1;
+  /// How many `GtkImage`s the switcher has *mapped*: a tab is its title and nothing else, so this
+  /// must be 0 -- an icon, or the missing-icon placeholder GTK draws for a page with no `icon-name`.
+  int dbg_switcher_images = -1;
   /// How many pages the sidebar stack holds: `pills` and `labels` must both equal it.
   int dbg_switcher_pages = -1;
   /// The switcher's own size, beside it: what the tab bar costs the column.
@@ -1560,6 +1563,11 @@ void config_dialog_refresh(ConfigDialog& d);
 void open_configurations(App& app);
 void save_layout_now(App& app);
 
+/// The sidebar's tabs are words: hide the icon every `AdwViewSwitcherButton` draws (the
+/// missing-icon placeholder, for a page with a title and no `icon-name`), for the buttons that exist
+/// and for any page added later. Call once, before `build_source_panels()`.
+void keep_tabs_icon_free(App& app);
+
 /// Capability panels (`src/ui_source.cpp`). `build_source_panels` adds the source kind's panels as
 /// pages of `side_stack`, once, before the first tick. `apply_source_panels` sets every panel's
 /// sensitivity from `connected` -- disabled, never hidden: the tab switcher owns visibility.