polish: row numbers, ping indicator, frozen column, keyboard nav

- ResultsPanel: _RowNumberProxy keeps vertical header numbers sequential
  in visual order (sort-stable); both views get a 48 px wide row-number header
- MainWindow: _PingWorker pings each active connection every 30 s via
  test_connection(); status dot (green/red) shown in status bar with tooltip
- TableViewer: 📌 toggle freezes first column using dual-view overlay
  (_frozen_view child widget) with synced scroll, row heights, and resize
  event-filter; column 0 is hidden in the main view while frozen
- RowDialog: OK set as default button; first field focused on open
- ConnectionDialog: OK set as default; Enter in password field submits

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/ui/table_viewer.py

@@ -16,7 +16,7 @@ from PyQt6.QtWidgets import (
     QMenu, QApplication,
 )
 from PyQt6.QtCore import (
-    Qt, QAbstractTableModel, QModelIndex, pyqtSignal,
+    Qt, QAbstractTableModel, QModelIndex, pyqtSignal, QEvent,
 )
 from PyQt6.QtGui import QColor, QBrush, QFont, QKeySequence, QShortcut
 
@@ -267,8 +267,15 @@ class RowDialog(QDialog):
         )
         bbox.accepted.connect(self.accept)
         bbox.rejected.connect(self.reject)
+        ok_btn = bbox.button(QDialogButtonBox.StandardButton.Ok)
+        if ok_btn:
+            ok_btn.setDefault(True)
         root.addWidget(bbox)
 
+        # Focus the first input field so the user can start typing immediately
+        if self._fields:
+            next(iter(self._fields.values())).setFocus()
+
     @property
     def values(self) -> dict:
         """Return {col: value_or_None} for all fields.
@@ -380,6 +387,13 @@ class TableViewer(QWidget):
         tb.addWidget(self._edit_btn)
         tb.addWidget(self._delete_btn)
         tb.addStretch()
+
+        self._freeze_btn = QPushButton("📌")
+        self._freeze_btn.setFixedWidth(34)
+        self._freeze_btn.setToolTip("Freeze first column (keep it visible while scrolling)")
+        self._freeze_btn.setCheckable(True)
+        self._freeze_btn.clicked.connect(self._toggle_freeze)
+        tb.addWidget(self._freeze_btn)
         root.addLayout(tb)
 
         # ── Table view ─────────────────────────────────────────────────────────
@@ -395,6 +409,7 @@ class TableViewer(QWidget):
             QHeaderView.ResizeMode.Interactive)
         self._table_view.horizontalHeader().setStretchLastSection(True)
         self._table_view.verticalHeader().setDefaultSectionSize(24)
+        self._table_view.verticalHeader().setFixedWidth(48)
         self._table_view.setContextMenuPolicy(
             Qt.ContextMenuPolicy.CustomContextMenu)
         self._table_view.customContextMenuRequested.connect(self._context_menu)
@@ -415,6 +430,40 @@ class TableViewer(QWidget):
                   self._delete_selected)
         QShortcut(QKeySequence("Ins"), self._table_view, self._add_row)
 
+        # ── Frozen first-column overlay ───────────────────────────────────────
+        self._freeze_active = False
+        self._frozen_view = QTableView(self._table_view)
+        self._frozen_view.setModel(self._model)
+        self._frozen_view.setFocusPolicy(Qt.FocusPolicy.NoFocus)
+        self._frozen_view.setVerticalScrollBarPolicy(
+            Qt.ScrollBarPolicy.ScrollBarAlwaysOff)
+        self._frozen_view.setHorizontalScrollBarPolicy(
+            Qt.ScrollBarPolicy.ScrollBarAlwaysOff)
+        self._frozen_view.setAlternatingRowColors(True)
+        self._frozen_view.verticalHeader().hide()
+        self._frozen_view.horizontalHeader().setSectionResizeMode(
+            QHeaderView.ResizeMode.Fixed)
+        self._frozen_view.setStyleSheet(
+            "QTableView { border: none; border-right: 2px solid #8caaee; }")
+        self._frozen_view.hide()
+
+        # Sync vertical scroll between the two views
+        self._table_view.verticalScrollBar().valueChanged.connect(
+            self._frozen_view.verticalScrollBar().setValue)
+        self._frozen_view.verticalScrollBar().valueChanged.connect(
+            self._table_view.verticalScrollBar().setValue)
+
+        # Sync row heights
+        self._table_view.verticalHeader().sectionResized.connect(
+            lambda row, _, h: self._frozen_view.setRowHeight(row, h))
+
+        # Update frozen geometry when column 0 is resized
+        self._table_view.horizontalHeader().sectionResized.connect(
+            lambda col, _old, _new: self._update_frozen_geometry() if col == 0 else None)
+
+        # Event filter to handle main view resize
+        self._table_view.installEventFilter(self)
+
         root.addWidget(self._table_view, 1)
 
         # ── Pagination bar (prominent, always visible) ─────────────────────────
@@ -505,11 +554,58 @@ class TableViewer(QWidget):
         self._refresh_action_states()
         self._table_view.resizeColumnsToContents()
         self._table_view.horizontalHeader().setStretchLastSection(True)
+        if self._freeze_active and self._model.columnCount() > 0:
+            self._apply_freeze()
 
     def _on_error(self, msg: str):
         self._total_lbl.setText(f"Error: {msg[:80]}")
         self.status_message.emit(f"Error: {msg}")
 
+    # ── Frozen column ──────────────────────────────────────────────────────────
+
+    def _toggle_freeze(self, checked: bool):
+        self._freeze_active = checked
+        if checked and self._model.columnCount() > 0:
+            self._apply_freeze()
+        elif not checked:
+            self._unapply_freeze()
+
+    def _apply_freeze(self):
+        col_count = self._model.columnCount()
+        if col_count == 0:
+            return
+        self._frozen_view.setSelectionModel(self._table_view.selectionModel())
+        for c in range(col_count):
+            self._frozen_view.setColumnHidden(c, c != 0)
+        self._frozen_view.resizeColumnToContents(0)
+        self._table_view.setColumnHidden(0, True)
+        self._update_frozen_geometry()
+        self._frozen_view.show()
+        self._frozen_view.raise_()
+
+    def _unapply_freeze(self):
+        self._frozen_view.hide()
+        if self._model.columnCount() > 0:
+            self._table_view.setColumnHidden(0, False)
+
+    def _update_frozen_geometry(self):
+        if not self._freeze_active:
+            return
+        fw     = self._table_view.frameWidth()
+        vh_w   = self._table_view.verticalHeader().width()
+        col0_w = self._frozen_view.columnWidth(0)
+        self._frozen_view.setGeometry(
+            fw + vh_w,
+            fw,
+            col0_w,
+            self._table_view.height() - 2 * fw,
+        )
+
+    def eventFilter(self, obj, event):
+        if obj is self._table_view and event.type() == QEvent.Type.Resize:
+            self._update_frozen_geometry()
+        return False
+
     def _refresh_pagination(self):
         ps = self._page_size if self._page_size > 0 else max(self._total, 1)
         rows_loaded   = self._model.rowCount()