refactor: streamline ThinkingBlock empty streaming handling

Remove the separate “Thinking…” placeholder component and embed the empty‑streaming state directly inside the main block. Adjust the click handler and button disabled logic to only allow toggling when content is available, preventing accidental collapse during loading. This change simplifies the component, eliminates duplicate markup, and improves UX by consistently showing the thinking indicator within the block.

web-app/src/containers/ThinkingBlock.tsx

@@ -107,27 +107,14 @@ const ThinkingBlock = ({
   // Determine if the block is truly empty (streaming started but no content/steps yet)
   const isStreamingEmpty = loading && N === 0
 
-  // If loading started but no content or steps have arrived yet, display the non-expandable 'Thinking...' block
-  if (isStreamingEmpty) {
-    return (
-      <div className="mx-auto w-full break-words">
-        <div className="mb-4 rounded-lg bg-main-view-fg/4 border border-dashed border-main-view-fg/10 p-2 flex items-center gap-3">
-          <Loader className="size-4 animate-spin text-main-view-fg/60" />
-          <span className="font-medium text-main-view-fg/80">
-            {t('chat:thinking')}
-          </span>
-        </div>
-      </div>
-    )
-  }
-
   // If not loading, and there are no steps, hide the block entirely.
   const hasContent = steps.length > 0
   if (!loading && !hasContent) return null
 
   const handleClick = () => {
     // Only allow toggling expansion if not currently loading
-    if (!loading) {
+    // Also only allow if there is content (to prevent collapsing the simple 'Thinking')
+    if (!loading && hasContent) {
       setThinkingState(id, !isExpanded)
     }
   }
@@ -265,7 +252,7 @@ const ThinkingBlock = ({
         }
       }
 
-      // Fallback if loading but no activeStep (isStreamingEmpty case, though handled before this memo)
+      // Fallback for isStreamingEmpty state (N=0)
       return `${t('chat:thinking')}`
     }
 
@@ -289,8 +276,9 @@ const ThinkingBlock = ({
 
   return (
     <div
-      className="mx-auto w-full cursor-pointer break-words"
-      onClick={handleClick}
+      className="mx-auto w-full break-words"
+      // Only set onClick handler if not loading AND we have content to expand
+      onClick={loading || !hasContent ? undefined : handleClick}
     >
       <div className="mb-4 rounded-lg bg-main-view-fg/4 p-2 transition-all duration-200">
         <div className="flex items-center gap-3">
@@ -299,11 +287,12 @@ const ThinkingBlock = ({
           )}
           <button
             className="flex items-center gap-2 focus:outline-none"
-            disabled={loading}
+            // Button is disabled/non-expandable if loading OR if there's no content to show
+            disabled={loading || !hasContent}
           >
             {/* Display chevron only if not loading AND steps exist to expand */}
             {!loading &&
-              steps.length > 0 &&
+              hasContent && // Use hasContent instead of steps.length > 0
               (isExpanded ? (
                 <ChevronUp className="size-4 text-main-view-fg/60 transition-transform duration-200" />
               ) : (
@@ -315,6 +304,14 @@ const ThinkingBlock = ({
           </button>
         </div>
 
+        {isStreamingEmpty && (
+          <div className="mt-2 pl-2 pr-4 text-main-view-fg/80">
+            <span className="font-medium text-main-view-fg/80">
+              {t('chat:thinking')}
+            </span>
+          </div>
+        )}
+
         {/* Streaming/Condensed View - shows active step (N-1) */}
         {loading && activeStep && (
           <div
@@ -342,7 +339,7 @@ const ThinkingBlock = ({
         )}
 
         {/* Expanded View - shows all steps */}
-        {isExpanded && !loading && (
+        {isExpanded && !loading && hasContent && (
           <div className="mt-4 pl-2 pr-4 text-main-view-fg/60 animate-in fade-in slide-in-from-top-2 duration-300">
             <div className="relative border-main-view-fg/20">
               {steps.map((step, index) => (