Fix recipe button unclickable on construction site during play

A selected construction site rebuilt the entire panel on every
TickAdvancedEvent (~30x/s at 1x), because refreshSelectionDisplay() called
rebuild() for sites. Each rebuild runs buildSingle() -> hideAllWidgets(),
which hides and re-shows the recipe-select button. Hiding a QPushButton
mid-press clears its pressed state, so a rebuild landing between the user's
mouse press and release cancelled the click. While paused no tick advances,
so no rebuild occurred and the button worked -- matching the report.

Give sites a lightweight per-tick refresh that updates only the progress
label, mirroring refreshBuffers() for live buildings. The site progress
block is extracted from buildSingle() into refreshSiteProgress() (no
duplicated arithmetic). refreshSelectionDisplay() now takes a RefreshReason:
a PeriodicTick updates progress only, while a CommandApplied still rebuilds
so a site's newly chosen recipe/layout is reflected. The site -> completed
building transition remains handled by the existing "(Building) " title
branch.

No UI test added: the test target links only lib (no QtWidgets), per the
simulation/presentation split, so a widget-level test does not fit the
harness.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DyCu8vwChKMbLJQ3xosYEN

src/ui/SelectedBuildingPanel.cpp

@@ -338,6 +338,16 @@ void SelectedBuildingPanel::buildSingle(BuildingId id)
 
     if (m_singleIsSite)
     {
+        refreshSiteProgress(s);
+    }
+    else
+    {
+        refreshBuffers(b);
+    }
+}
+
+void SelectedBuildingPanel::refreshSiteProgress(const ConstructionSite* s)
+{
     QString progress;
     if (s->completesAt == 0)
     {
@@ -364,11 +374,6 @@ void SelectedBuildingPanel::buildSingle(BuildingId id)
         }
     }
     m_buffersLabel->setText(progress);
-    }
-    else
-    {
-        refreshBuffers(b);
-    }
 }
 
 void SelectedBuildingPanel::refreshBuffers(const Building* b)
@@ -562,7 +567,7 @@ const ShipDef* SelectedBuildingPanel::findShipDef(const std::string& id) const
 
 void SelectedBuildingPanel::handleEvent(std::shared_ptr<const TickAdvancedEvent> /*event*/)
 {
-    refreshSelectionDisplay();
+    refreshSelectionDisplay(RefreshReason::PeriodicTick);
 }
 
 void SelectedBuildingPanel::handleEvent(
@@ -572,10 +577,10 @@ void SelectedBuildingPanel::handleEvent(
     // queued drain, not synchronously. When the game is paused no tick advances,
     // so TickAdvancedEvent never fires; refresh here too, otherwise the panel
     // would not reflect the change until the next tick or a re-selection.
-    refreshSelectionDisplay();
+    refreshSelectionDisplay(RefreshReason::CommandApplied);
 }
 
-void SelectedBuildingPanel::refreshSelectionDisplay()
+void SelectedBuildingPanel::refreshSelectionDisplay(RefreshReason reason)
 {
     if (m_selectedEntity.has_value())
     {
@@ -599,8 +604,19 @@ void SelectedBuildingPanel::refreshSelectionDisplay()
     }
     const ConstructionSite* s = m_sim->buildings().findSite(m_singleBuildingId);
     if (s)
+    {
+        // A periodic tick only advances construction progress, so update just the
+        // progress label. Rebuilding every tick would hide/re-show all widgets and
+        // cancel any in-progress click on the recipe button. An applied command
+        // may have changed the site's recipe/layout, so rebuild in that case.
+        if (reason == RefreshReason::CommandApplied)
         {
             rebuild();
+        }
+        else
+        {
+            refreshSiteProgress(s);
+        }
         return;
     }
     buildEmpty();

src/ui/SelectedBuildingPanel.h

@@ -59,8 +59,18 @@ private slots:
     void onSplitterFilterChanged();
 
 private:
+    // Why the selection display is being refreshed. A periodic tick only needs a
+    // lightweight content update (e.g. a construction site's progress label),
+    // whereas an applied player command may have changed the configuration and
+    // needs a full structural rebuild.
+    enum class RefreshReason
+    {
+        PeriodicTick,
+        CommandApplied
+    };
+
     void onSelectionChanged(const std::vector<BuildingId>& ids);
-    void refreshSelectionDisplay();
+    void refreshSelectionDisplay(RefreshReason reason);
     void rebuild();
     void hideAllWidgets();
     void clearContent();
@@ -68,6 +78,7 @@ private:
     void buildSingle(BuildingId id);
     void buildMulti(const std::vector<BuildingId>& ids);
     void refreshBuffers(const Building* b);
+    void refreshSiteProgress(const ConstructionSite* s);
     void updateShipyardLayoutWidgets(BuildingType type,
                                      const std::string& recipeId,
                                      const std::optional<ShipLayoutConfig>& shipLayout);