ui: the readouts show in a strip under the plot when the dock is hidden

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

src/ui_widgets.cpp

@@ -79,6 +79,8 @@ void install_css() {
       ".udpscope-badge { padding: 2px 12px; min-height: 0; border-radius: 14px; }\n"
       ".udpscope-badge-open { background-color: alpha(@accent_bg_color, 0.28); }\n"
       ".udpscope-badge-state { opacity: 0.7; }\n"
+      // The readouts strip's two text buttons: Adwaita's 34 px button would be taller than the strip.
+      "button.udpscope-strip-button { min-height: 0; padding: 1px 8px; }\n"
       // The contextual-help "(i)": a *mark*, not a button. Adwaita's menu button is a 34x34 control
       // (a 24 px floor plus 5 px of padding) with a 16 px glyph, which beside a heading reads as a
       // second toolbar button. Measured on libadwaita 1.10: the outer `menubutton` node *and* its