Feat: Modify the style of the agent page bright theme #3221 (#9162)

### What problem does this PR solve?

Feat: Modify the style of the agent page bright theme #3221

### Type of change


- [x] New Feature (non-breaking change which adds functionality)

web/src/pages/agent/canvas/node/dropdown/next-step-dropdown.tsx

@@ -60,7 +60,7 @@ function AccordionOperators() {
       defaultValue={['item-1', 'item-2', 'item-3', 'item-4', 'item-5']}
     >
       <AccordionItem value="item-1">
-        <AccordionTrigger className="text-xl">AI</AccordionTrigger>
+        <AccordionTrigger className="text-xl">Foundation</AccordionTrigger>
         <AccordionContent className="flex flex-col gap-4 text-balance">
           <OperatorItemList
             operators={[Operator.Agent, Operator.Retrieval]}

web/src/pages/agent/canvas/node/handle.tsx

@@ -36,7 +36,7 @@ export function CommonHandle({
           showModal();
         }}
       >
-        <Plus className="size-3 pointer-events-none" />
+        <Plus className="size-3 pointer-events-none text-text-title-invert" />
         {visible && (
           <InnerNextStepDropdown hideModal={hideModal}>
             <span></span>