fix: email selection in table view + responsive filter bar

- Connect currentRowChanged to onRowSelected so single-click in table shows email in reader
- Add responsive filter bar: hide groupBy/displayMode/pivot combos progressively as width decreases
- Set Fixed size policy on combos to prevent unwanted stretching
- Reduced filter layout spacing from 12 to 8px

src/ui/maillistview.cpp

@@ -72,24 +72,29 @@ void MailListView::setupUI()
     QWidget *filterBar = new QWidget();
     filterBar->setFixedHeight(36);
     filterBar->setStyleSheet("background-color: #f5f5f7; border-bottom: 1px solid #d1d1d6;");
+    filterBar->setObjectName("filterBar");
     QHBoxLayout *filterLayout = new QHBoxLayout(filterBar);
     filterLayout->setContentsMargins(12, 2, 12, 2);
-    filterLayout->setSpacing(12);
+    filterLayout->setSpacing(8);
 
     m_unreadOnlyCheck = new QCheckBox("No leídos");
     m_unreadOnlyCheck->setStyleSheet("QCheckBox { font-size: 12px; color: #333; }");
+    m_unreadOnlyCheck->setObjectName("filterCheck");
     filterLayout->addWidget(m_unreadOnlyCheck);
 
     m_flaggedOnlyCheck = new QCheckBox("Marcados");
     m_flaggedOnlyCheck->setStyleSheet("QCheckBox { font-size: 12px; color: #333; }");
+    m_flaggedOnlyCheck->setObjectName("filterCheck");
     filterLayout->addWidget(m_flaggedOnlyCheck);
 
     m_hasAttachmentsCheck = new QCheckBox("Con adjuntos");
     m_hasAttachmentsCheck->setStyleSheet("QCheckBox { font-size: 12px; color: #333; }");
+    m_hasAttachmentsCheck->setObjectName("filterCheck");
     filterLayout->addWidget(m_hasAttachmentsCheck);
 
     m_pinnedOnlyCheck = new QCheckBox("Solo fijados");
     m_pinnedOnlyCheck->setStyleSheet("QCheckBox { font-size: 12px; color: #333; }");
+    m_pinnedOnlyCheck->setObjectName("filterCheck");
     filterLayout->addWidget(m_pinnedOnlyCheck);
 
     filterLayout->addStretch();
@@ -99,6 +104,7 @@ void MailListView::setupUI()
     m_pivotCombo->addItem("Principal");  // Focused
     m_pivotCombo->addItem("Otros");      // Other
     m_pivotCombo->setFixedWidth(140);
+    m_pivotCombo->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
     m_pivotCombo->setStyleSheet(
         "QComboBox { border: 1px solid #d1d1d6; border-radius: 4px; padding: 4px 8px; "
         "background: white; min-height: 20px; }"
@@ -116,6 +122,7 @@ void MailListView::setupUI()
     m_displayModeCombo->addItem("Medio");
     m_displayModeCombo->addItem("Espacioso");
     m_displayModeCombo->setFixedWidth(120);
+    m_displayModeCombo->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
     m_displayModeCombo->setStyleSheet(
         "QComboBox { border: 1px solid #d1d1d6; border-radius: 4px; padding: 4px 8px; "
         "background: white; min-height: 20px; }"
@@ -133,6 +140,7 @@ void MailListView::setupUI()
     m_groupByCombo->addItem("Agrupar por conversación");
     m_groupByCombo->addItem("Agrupar por remitente");
     m_groupByCombo->setFixedWidth(180);
+    m_groupByCombo->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
     m_groupByCombo->setStyleSheet(
         "QComboBox { border: 1px solid #d1d1d6; border-radius: 4px; padding: 4px 8px; "
         "background: white; min-height: 20px; }"
@@ -249,6 +257,9 @@ void MailListView::setupUI()
 
     connect(m_treeView->selectionModel(), &QItemSelectionModel::selectionChanged,
             this, &MailListView::onSelectionChanged);
+    // Single-click selection in tree view -> emit emailSelected for reader pane
+    connect(m_treeView->selectionModel(), &QItemSelectionModel::currentRowChanged,
+            this, &MailListView::onRowSelected);
     connect(m_treeView, &QTreeView::doubleClicked, this, [this](const QModelIndex &index) {
         if (!index.isValid()) return;
         QModelIndex proxyIdx = m_proxyModel->mapToSource(index);
@@ -385,6 +396,22 @@ void MailListView::updateViewMode()
             m_treeView->header()->show();
         }
     }
+    
+    // Also update filter bar responsiveness
+    updateFilterBarVisibility(viewportWidth);
+}
+
+void MailListView::updateFilterBarVisibility(int viewportWidth)
+{
+    // Hide controls progressively as width decreases
+    // Thresholds: show all > 900px, hide groupBy > 750px, hide displayMode > 600px, hide pivot > 500px
+    bool showGroupBy = viewportWidth > 750;
+    bool showDisplayMode = viewportWidth > 600;
+    bool showPivot = viewportWidth > 500;
+    
+    m_groupByCombo->setVisible(showGroupBy);
+    m_displayModeCombo->setVisible(showDisplayMode);
+    m_pivotCombo->setVisible(showPivot && m_pivotCombo->isVisible()); // respect folder-type visibility
 }
 
 QVector<int> MailListView::getSelectedMailIds() const

src/ui/maillistview.h

@@ -94,6 +94,7 @@ private:
     void setupUI();
     void refreshViews();
     void updateViewMode();
+    void updateFilterBarVisibility(int viewportWidth);  // New: responsive filter bar
     void updateActionBar();
     QVector<int> getSelectedMailIds() const;
     void initDrag();