explain an item wherever the UI names one

Every display naming an item now shows that item's production tooltip, not
only the selection panel's chips: the header block stock, the total cost of
a building multi-selection, the remaining scrap of a debris selection, the
icons of every recipe summary, and a blueprint card's cost.

ItemTooltip moves out of the selection panel and takes an
ItemTooltipContext of its own -- an item is named all over the UI, and the
panel's context carries visuals and a debug flag no tooltip reads. A
recipe line wraps each icon with its amount so the pair can be pointed at
as one statement, and attaches tooltips only where asked: a module button
and the item tooltip itself draw the same line and stay silent.

Hover only wherever the display sits on something the player clicks, whose
click is not free to explain. Note that a recipe line on an option button
can no longer be transparent to the mouse -- Qt never looks inside a
transparent widget for the cursor -- so it relies on press propagation to
keep picking the option.

The header block stock loses world.building_blocks_tooltip, showing what
every other block icon shows instead. The Expand button keeps no tooltip:
its cost is painted into its face with nowhere to hang one, and the button
is due to be removed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ne3mejABZoLWKLh8fgpM3x

src/ui/ItemTooltip.cpp

@@ -0,0 +1,102 @@
+#include "ItemTooltip.h"
+
+#include <QFont>
+#include <QLabel>
+#include <QVBoxLayout>
+
+#include "DisplayName.h"
+#include "GameConfig.h"
+#include "ItemProducers.h"
+#include "RecipeLineRow.h"
+#include "RecipesConfig.h"
+#include "Simulation.h"
+
+namespace
+{
+
+std::vector<RecipeLineRow::Amount> toAmounts(
+    const std::vector<RecipeIngredient>& ingredients)
+{
+    std::vector<RecipeLineRow::Amount> amounts;
+    amounts.reserve(ingredients.size());
+    for (const RecipeIngredient& ingredient : ingredients)
+    {
+        amounts.push_back(RecipeLineRow::Amount{ ingredient.item, ingredient.amount });
+    }
+    return amounts;
+}
+
+}  // namespace
+
+
+void ItemTooltip::attachTo(QWidget& target, const ItemTooltipContext& context,
+                           const std::string& itemId, TooltipTrigger::Trigger trigger)
+{
+    ItemTooltip* tooltip = new ItemTooltip(context, itemId, &target);
+    TooltipTrigger::attach(target, *tooltip, trigger);
+}
+
+ItemTooltip::ItemTooltip(const ItemTooltipContext& context, const std::string& itemId,
+                         QWidget* parent)
+    : Tooltip(parent)
+    , m_context(context)
+    , m_itemId(itemId)
+{
+}
+
+void ItemTooltip::refreshContent()
+{
+    clearContent();
+    QVBoxLayout* layout = getContentLayout();
+
+    // The heading names the item. For an input chip this is the only place it is named
+    // at all, since such a chip carries a count and no name (REQ-UI-SINGLE-SELECTION).
+    QLabel* heading =
+        new QLabel(QString::fromStdString(toDisplayName(m_itemId)), this);
+    QFont headingFont = heading->font();
+    headingFont.setBold(true);
+    heading->setFont(headingFont);
+    layout->addWidget(heading);
+    heading->show();
+
+    const ItemProduction production =
+        findItemProduction(m_itemId, *m_context.sim, *m_context.config);
+
+    // Scrap is salvaged from debris rather than crafted (REQ-RES-DEBRIS-DROP), so it
+    // says where it comes from in place of the caption and lists nothing.
+    QLabel* caption = new QLabel(production.origin == ItemOrigin::Salvaged
+        ? tr("Salvaged from debris")
+        : tr("Produced by"), this);
+    layout->addWidget(caption);
+    caption->show();
+
+    if (production.origin == ItemOrigin::Undiscovered)
+    {
+        // Made somehow, but by nothing the player has unlocked -- named without being
+        // shown a path they cannot take yet (REQ-UI-ITEM-TOOLTIP).
+        QLabel* undiscovered = new QLabel(tr("Undiscovered"), this);
+        layout->addWidget(undiscovered);
+        undiscovered->show();
+        return;
+    }
+
+    for (const RecipeDef* recipe : production.recipes)
+    {
+        RecipeLineRow::Spec spec;
+        spec.building        = recipe->building;
+        spec.name            = QString::fromStdString(toDisplayName(recipe->id));
+        spec.inputs          = toAmounts(recipe->inputs);
+        spec.outputGroups    = RecipeLineRow::toOutputGroups(*recipe);
+        spec.durationSeconds = recipe->durationSeconds;
+
+        // Boxed, because an item with several producers stacks several of these and a run
+        // of bare lines reads as one field of icons (REQ-UI-ITEM-TOOLTIP). The items it
+        // names carry no tooltip of their own: this is already one
+        // (REQ-UI-ITEM-VALUE-TOOLTIP).
+        RecipeLineRow* line =
+            new RecipeLineRow(m_context.itemIcons, m_context.buildingIcons, this);
+        line->setCardChrome(true);
+        layout->addWidget(line);
+        line->setLine(spec);
+    }
+}