give the selection cards their own parts instead of label blobs

src/ui/selection/StatusPill.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include <QColor>
+#include <QString>
+#include <QWidget>
+
+class QLabel;
+
+// The card header's right slot (REQ-UI-SELECTION-CARD): a colored dot with a short
+// caption beside it. It carries a building's production status
+// (REQ-UI-SELECTION-STATUS), a ship's current behavior (REQ-UI-SHIP-BEHAVIOR), or an
+// aggregated selection's object count (REQ-UI-SELECTION-AGGREGATE) -- never more than
+// one of them, which is why they share one part.
+class StatusPill : public QWidget
+{
+    Q_OBJECT
+
+public:
+    explicit StatusPill(QWidget* parent = nullptr);
+
+    // An invalid dot color leaves the dot off, for the slots that are a plain caption.
+    // An empty caption hides the pill entirely.
+    void setStatus(const QColor& dotColor, const QColor& outlineColor,
+                   const QString& caption);
+
+private:
+    QLabel* m_dotLabel;
+    QLabel* m_captionLabel;
+};