fix(chat): keep a stable Thinking… label instead of cycling phase text

Greptile flagged that phase text repeatedly re-announces to assistive tech
during a single pending stream; a static label avoids the repeated
live-region updates while keeping the gooey shape morph.

Author: waleedlatif1

apps/sim/app/workspace/[workspaceId]/home/components/message-content/components/special-tags/special-tags.tsx

@@ -430,7 +430,7 @@ export function SpecialTags({
 export function PendingTagIndicator() {
   return (
     <div className='animate-stream-fade-in py-2'>
-      <ThinkingLoader size={20} startVariant='corners' phase labelRatio={0.7} />
+      <ThinkingLoader size={20} startVariant='corners' label='Thinking…' labelRatio={0.7} />
     </div>
   )
 }