feat: value history timestamps, Ctrl+F search, base address fixes

- Add timestamps to ValueHistory ring buffer, expose via new MCP tool
  node.history, show relative time in popup ("26s ago", "2m ago")
- Add "Clear Value History" right-click menu for single and multi-select
- Add Ctrl+F find bar to RcxEditor with live search, Enter-to-next, wrap
- Fix Ctrl+F in workspace dock to auto-focus search field
- Add "Change to float" quick-convert for Hex32 right-click menu
- Sort workspace explorer by children count descending (most fields first)
- Fix provider->base() overwriting saved base address from .rcx files
- Add formula support to MCP change_base operation
- Re-evaluate baseAddressFormula on provider attach in selectSource()

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

src/main.cpp

@@ -2737,6 +2737,18 @@ void MainWindow::createWorkspaceDock() {
         }
     });
 
+    // Ctrl+F focuses the workspace search field
+    {
+        auto* findAction = new QAction(dockContainer);
+        findAction->setShortcut(QKeySequence::Find);
+        findAction->setShortcutContext(Qt::WidgetWithChildrenShortcut);
+        dockContainer->addAction(findAction);
+        connect(findAction, &QAction::triggered, this, [this]() {
+            m_workspaceSearch->setFocus();
+            m_workspaceSearch->selectAll();
+        });
+    }
+
     m_workspaceDock->setWidget(dockContainer);
     addDockWidget(Qt::LeftDockWidgetArea, m_workspaceDock);
     m_workspaceDock->hide();