implement artifact win condition (REQ-WIN-ARTIFACT-COUNT, REQ-WIN-SCREEN)

- Add [artifacts] config section to world.toml with artifact_chance_formula (x = station level) and artifact_win_count
- Roll artifact chance before each schematic drop; on success show 2 schematics + Artifact option instead of 3
- Selecting Artifact increments artifact count; reaching artifact_win_count triggers win screen
- Display "Artifacts: x/y" in header bar via ArtifactCountChangedEvent
- Win screen mirrors game-over screen with "Won!" caption and same Restart/Quit buttons

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DUsFgd2Ga6pmLz8giS8WUn

src/ui/MainWindow.cpp

@@ -313,3 +313,42 @@ void MainWindow::handleEvent(std::shared_ptr<const GameOverEvent> /*event*/)
         close();
     }
 }
+
+void MainWindow::handleEvent(std::shared_ptr<const WinEvent> /*event*/)
+{
+    const Tick tick = m_sim->currentTick();
+    const int totalSeconds = static_cast<int>(ticksToSeconds(tick));
+    const int minutes = totalSeconds / 60;
+    const int seconds = totalSeconds % 60;
+
+    QMessageBox box(this);
+    box.setWindowTitle(tr("Won!"));
+    box.setText(tr("You collected all artifacts!\nSurvival time: %1:%2")
+        .arg(minutes, 2, 10, QChar('0'))
+        .arg(seconds, 2, 10, QChar('0')));
+    QPushButton* restartBtn = box.addButton(tr("Restart"), QMessageBox::AcceptRole);
+    box.addButton(tr("Quit"), QMessageBox::RejectRole);
+    box.exec();
+
+    if (box.clickedButton() == restartBtn)
+    {
+        try
+        {
+            GameConfig newConfig = ConfigLoader::loadFromDirectory(m_configDir);
+            VisualsConfig newVisuals = VisualsLoader::load(m_configDir + "/visuals.toml");
+            m_visuals = std::move(newVisuals);
+            m_sim->reset(std::move(newConfig));
+        }
+        catch (const std::exception& e)
+        {
+            QMessageBox::critical(this, tr("Config Error"),
+                tr("Failed to reload config:\n%1").arg(e.what()));
+            return;
+        }
+        m_gameWorldView->resetForNewGame();
+    }
+    else
+    {
+        close();
+    }
+}