fix: enable text selection in results panel and preserve AI prompt

Add select-text to override global user-select:none on results table,
JSON view, error messages, and AI explanation. Also keep AI prompt text
after generation with a clear button.

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

src/components/ai/AiBar.tsx

@@ -3,7 +3,7 @@ import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
 import { AiSettingsPopover } from "./AiSettingsPopover";
 import { useGenerateSql } from "@/hooks/use-ai";
-import { Sparkles, Loader2, X } from "lucide-react";
+import { Sparkles, Loader2, X, Eraser } from "lucide-react";
 import { toast } from "sonner";
 
 interface Props {
@@ -24,7 +24,6 @@ export function AiBar({ connectionId, onSqlGenerated, onClose, onExecute }: Prop
       {
         onSuccess: (sql) => {
           onSqlGenerated(sql);
-          setPrompt("");
         },
         onError: (err) => {
           toast.error("AI generation failed", { description: String(err) });
@@ -77,6 +76,18 @@ export function AiBar({ connectionId, onSqlGenerated, onClose, onExecute }: Prop
           "Generate"
         )}
       </Button>
+      {prompt.trim() && (
+        <Button
+          size="sm"
+          variant="ghost"
+          className="h-6 w-6 p-0"
+          onClick={() => setPrompt("")}
+          title="Clear prompt"
+          disabled={generateMutation.isPending}
+        >
+          <Eraser className="h-3 w-3" />
+        </Button>
+      )}
       <AiSettingsPopover />
       <Button
         size="sm"