fix: prevent pipeline step settings from resetting on collapse

The settings panel used conditional rendering ({isExpanded && ...})
which unmounted the Controls component on collapse, losing all state.
Switch to CSS hidden class so the component stays mounted and settings
persist when the panel is collapsed and re-expanded.

apps/web/src/components/tools/pipeline-builder.tsx

@@ -284,9 +284,12 @@ export function PipelineBuilder({
                   </div>
                 </div>
 
-                {/* Expanded settings */}
+                {/* Settings panel - hidden when collapsed, never unmounted so state persists */}
-                {isExpanded && (
+                <div
-                  <div className="border-t border-border p-3 bg-muted/10 space-y-3">
+                  className={
+                    isExpanded ? "border-t border-border p-3 bg-muted/10 space-y-3" : "hidden"
+                  }
+                >
                   <p className="text-xs text-muted-foreground">{tool.description}</p>
                   <PipelineStepSettings
                     toolId={step.toolId}
@@ -294,7 +297,6 @@ export function PipelineBuilder({
                     onChange={(s) => updateStepSettings(step.id, s)}
                   />
                 </div>
-                )}
               </div>
             );
           })