feat: shortcuts dialog, tab context menus, smart status bar, recent files

- ShortcutsDialog: grouped tree of all keyboard shortcuts (Help menu)
- Workspace tab context menu: Rename, Close, Close Others, Close to Right
- SQL query tab context menu: Rename, Duplicate, Close, Close Others
- Smart status bar: right-side connection indicator + selected cell preview
- File → Open SQL File (Ctrl+O), Save (Ctrl+S), Save As, Open Recent
- Recent files persisted to ~/.dbclient/recent_files.json (last 10)
- TableViewer.cell_selected signal wired to status bar cell preview
- EditorTab._filepath tracks the file associated with each query tab

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

app/ui/sql_editor.py

@@ -6,6 +6,7 @@ from PyQt6.QtWidgets import (
     QWidget, QVBoxLayout, QHBoxLayout, QPlainTextEdit, QTextEdit,
     QTabWidget, QPushButton, QLabel, QSplitter, QTabBar, QSizePolicy,
     QFileDialog, QMessageBox, QToolButton, QComboBox, QLineEdit, QCheckBox,
+    QMenu, QInputDialog,
 )
 from PyQt6.QtCore import Qt, QRect, QSize, pyqtSignal, QTimer
 from PyQt6.QtGui import (
@@ -404,6 +405,7 @@ class EditorTab(QWidget):
         self._driver   = driver
         self._database = database
         self._worker: QueryWorker | None = None
+        self._filepath: str | None = None
         self._build_ui()
 
     def _build_ui(self):
@@ -582,6 +584,14 @@ class SQLEditorWidget(QWidget):
         new_btn.clicked.connect(lambda: self.new_tab())
         self._tabs.setCornerWidget(new_btn, Qt.Corner.TopRightCorner)
 
+        # Right-click context menu on query tab bar
+        self._tabs.tabBar().setContextMenuPolicy(
+            Qt.ContextMenuPolicy.CustomContextMenu
+        )
+        self._tabs.tabBar().customContextMenuRequested.connect(
+            self._tab_context_menu
+        )
+
         root.addWidget(self._tabs)
 
     def new_tab(self, driver=None, database: str = "",
@@ -599,6 +609,44 @@ class SQLEditorWidget(QWidget):
         if self._tabs.count() > 1:
             self._tabs.removeTab(idx)
 
+    def _tab_context_menu(self, pos) -> None:
+        idx = self._tabs.tabBar().tabAt(pos)
+        if idx < 0:
+            return
+        menu = QMenu(self)
+        rename_act   = menu.addAction("Rename…")
+        dup_act      = menu.addAction("Duplicate")
+        menu.addSeparator()
+        close_act    = menu.addAction("Close")
+        close_others = menu.addAction("Close Others")
+
+        close_act.setEnabled(self._tabs.count() > 1)
+        close_others.setEnabled(self._tabs.count() > 1)
+
+        act = menu.exec(self._tabs.tabBar().mapToGlobal(pos))
+        if act == rename_act:
+            text, ok = QInputDialog.getText(
+                self, "Rename Tab", "Tab name:",
+                text=self._tabs.tabText(idx),
+            )
+            if ok and text.strip():
+                self._tabs.setTabText(idx, text.strip())
+        elif act == dup_act:
+            tab = self._tabs.widget(idx)
+            if isinstance(tab, EditorTab):
+                new = self.new_tab(
+                    tab._driver, tab._database,
+                    sql=tab.get_sql(),
+                    title=self._tabs.tabText(idx) + " (copy)",
+                )
+                new._filepath = tab._filepath
+        elif act == close_act:
+            self._close_tab(idx)
+        elif act == close_others:
+            for i in range(self._tabs.count() - 1, -1, -1):
+                if i != idx:
+                    self._close_tab(i)
+
     def current_tab(self) -> EditorTab | None:
         w = self._tabs.currentWidget()
         return w if isinstance(w, EditorTab) else None