fix: preserve tab state when switching between tabs

Render all tabs simultaneously with display:none for inactive ones,
instead of conditionally rendering only the active tab. This prevents
React from unmounting/remounting components on tab switch, preserving
query results, editor cursor, AI explanations, and other local state.

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

src/components/workspace/TabContent.tsx

@@ -8,9 +8,8 @@ import { EntityLookupPanel } from "@/components/lookup/EntityLookupPanel";
 
 export function TabContent() {
   const { tabs, activeTabId, updateTab } = useAppStore();
-  const activeTab = tabs.find((t) => t.id === activeTabId);
 
-  if (!activeTab) {
+  if (tabs.length === 0) {
     return (
       <div className="flex h-full items-center justify-center text-sm text-muted-foreground">
         Open a query tab or select a table to get started.
@@ -18,56 +17,75 @@ export function TabContent() {
     );
   }
 
-  switch (activeTab.type) {
-    case "query":
-      return (
-        <WorkspacePanel
-          key={activeTab.id}
-          connectionId={activeTab.connectionId}
-          initialSql={activeTab.sql}
-          onSqlChange={(sql) => updateTab(activeTab.id, { sql })}
-        />
-      );
-    case "table":
-      return (
-        <TableDataView
-          key={activeTab.id}
-          connectionId={activeTab.connectionId}
-          schema={activeTab.schema!}
-          table={activeTab.table!}
-        />
-      );
-    case "structure":
-      return (
-        <TableStructure
-          key={activeTab.id}
-          connectionId={activeTab.connectionId}
-          schema={activeTab.schema!}
-          table={activeTab.table!}
-        />
-      );
-    case "roles":
-      return (
-        <RoleManagerView
-          key={activeTab.id}
-          connectionId={activeTab.connectionId}
-        />
-      );
-    case "sessions":
-      return (
-        <SessionsView
-          key={activeTab.id}
-          connectionId={activeTab.connectionId}
-        />
-      );
-    case "lookup":
-      return (
-        <EntityLookupPanel
-          key={activeTab.id}
-          connectionId={activeTab.connectionId}
-        />
-      );
-    default:
-      return null;
-  }
+  return (
+    <>
+      {tabs.map((tab) => {
+        const isActive = tab.id === activeTabId;
+        let content: React.ReactNode;
+
+        switch (tab.type) {
+          case "query":
+            content = (
+              <WorkspacePanel
+                connectionId={tab.connectionId}
+                initialSql={tab.sql}
+                onSqlChange={(sql) => updateTab(tab.id, { sql })}
+              />
+            );
+            break;
+          case "table":
+            content = (
+              <TableDataView
+                connectionId={tab.connectionId}
+                schema={tab.schema!}
+                table={tab.table!}
+              />
+            );
+            break;
+          case "structure":
+            content = (
+              <TableStructure
+                connectionId={tab.connectionId}
+                schema={tab.schema!}
+                table={tab.table!}
+              />
+            );
+            break;
+          case "roles":
+            content = (
+              <RoleManagerView
+                connectionId={tab.connectionId}
+              />
+            );
+            break;
+          case "sessions":
+            content = (
+              <SessionsView
+                connectionId={tab.connectionId}
+              />
+            );
+            break;
+          case "lookup":
+            content = (
+              <EntityLookupPanel
+                connectionId={tab.connectionId}
+              />
+            );
+            break;
+          default:
+            content = null;
+        }
+
+        return (
+          <div
+            key={tab.id}
+            className="h-full"
+            style={{ display: isActive ? undefined : "none" }}
+          >
+            {content}
+          </div>
+        );
+      })}
+    </>
+  );
 }