fix(site/src/pages/AgentsPage): align thinking disclosure (#24743)

The agent chat thinking disclosure used a smaller label with the caret
on the left, which made collapsed and in-progress thinking look
different from collapsible tool calls.

Align the thinking disclosure with the shared tool-call row treatment by
using the same label size, trailing caret placement, and hover color
while preserving the streaming shimmer. Adds a Storybook story that
renders collapsed thinking next to a tool call.

<details>
<summary>Storybook screenshots</summary>

Captured from Storybook:

-
`pages/AgentsPage/ChatConversation/ConversationTimeline/ThinkingBlockWithToolCall`
-
`pages/AgentsPage/ChatConversation/ConversationTimeline/ThinkingBlockWithToolCall`
hovered
-
`pages/AgentsPage/ChatConversation/StreamingOutput/ThinkingDuringStreamingWithToolCalls`

Screenshots are attached in the Coder task.

</details>

Generated by Coder Agents.

site/src/pages/AgentsPage/components/ChatConversation/ConversationTimeline.stories.tsx

@@ -1768,6 +1768,64 @@ export const ThinkingBlockAlwaysCollapsed: Story = {
 	},
 };
 
+/** Collapsed thinking should visually align with adjacent tool calls. */
+export const ThinkingBlockWithToolCall: Story = {
+	parameters: {
+		queries: [
+			{
+				key: ["me", "preferences"],
+				data: {
+					task_notification_alert_dismissed: false,
+					thinking_display_mode: "always_collapsed" as const,
+				},
+			},
+		],
+	},
+	args: {
+		...defaultArgs,
+		parsedMessages: buildMessages([
+			{
+				...baseMessage,
+				id: 1,
+				role: "assistant",
+				content: [
+					{
+						type: "reasoning",
+						text: "I need to inspect the package metadata before answering.",
+					},
+					{
+						type: "tool-call",
+						tool_call_id: "tool-1",
+						tool_name: "read_file",
+						args: { path: "package.json" },
+					},
+				],
+			},
+			{
+				...baseMessage,
+				id: 2,
+				role: "tool",
+				content: [
+					{
+						type: "tool-result",
+						tool_call_id: "tool-1",
+						result: { content: '{"name":"coder"}' },
+					},
+				],
+			},
+		]),
+	},
+	play: async ({ canvasElement }) => {
+		const canvas = within(canvasElement);
+		expect(
+			canvas.getByRole("button", { name: /thinking/i }),
+		).toBeInTheDocument();
+		expect(
+			canvas.getByRole("button", { name: /read package\.json/i }),
+		).toBeInTheDocument();
+	},
+};
+
 /**
  * A completed thinking block with auto mode should be collapsed
  * (non-streaming state means auto collapses).

site/src/pages/AgentsPage/components/ChatConversation/ConversationTimeline.tsx

@@ -154,31 +154,31 @@ const ReasoningDisclosure = memo<{
 			>
 				<CollapsibleTrigger
 					className={cn(
-						"border-0 bg-transparent p-0 m-0 font-[inherit] text-left",
-						"flex w-full items-center gap-1.5 cursor-pointer",
+						"border-0 bg-transparent p-0 m-0 font-[inherit] text-[inherit] text-left",
+						"flex w-full items-center gap-2 cursor-pointer",
 						"text-content-secondary transition-colors hover:text-content-primary",
 					)}
 				>
-					<ChevronDownIcon
-						className={cn(
-							"size-icon-sm shrink-0 transition-transform",
-							expanded ? "rotate-0" : "-rotate-90",
-						)}
-					/>
 					{isStreaming ? (
-						<Shimmer as="span" className="text-xs">
+						<Shimmer as="span" className="text-sm">
 							Thinking
 						</Shimmer>
 					) : (
-						<span className="text-xs">Thinking</span>
+						<span className="text-sm">Thinking</span>
 					)}
+					<ChevronDownIcon
+						className={cn(
+							"ml-auto h-3 w-3 shrink-0 text-current transition-transform",
+							expanded ? "rotate-0" : "-rotate-90",
+						)}
+					/>
 				</CollapsibleTrigger>
 				{hasText && (
 					<CollapsibleContent>
 						<div
 							ref={previewScrollRef}
 							className={cn(
-								"mt-1 pl-5",
+								"mt-1.5",
 								isPreviewConstrained && "max-h-24 overflow-y-auto",
 							)}
 						>

site/src/pages/AgentsPage/components/ChatConversation/StreamingOutput.tsx

@@ -33,9 +33,11 @@ const hasTextOrReasoningBlock = (blocks: readonly RenderBlock[]): boolean =>
  * collapsible thinking disclosure label.
  */
 const StreamingThinkingPlaceholder: FC = () => (
-	<Shimmer as="span" className="text-xs text-content-secondary">
-		Thinking
-	</Shimmer>
+	<div className="flex w-full items-center gap-2 py-0.5 text-content-secondary">
+		<Shimmer as="span" className="text-sm">
+			Thinking
+		</Shimmer>
+	</div>
 );
 
 export const StreamingOutput: FC<{

site/src/pages/AgentsPage/components/ChatElements/tools/ToolCollapsible.tsx

@@ -31,13 +31,14 @@ export const ToolCollapsible: FC<ToolCollapsibleProps> = ({
 					className={cn(
 						"border-0 bg-transparent p-0 m-0 font-[inherit] text-[inherit] text-left",
 						"flex w-full items-center gap-2 cursor-pointer",
+						"text-content-secondary transition-colors hover:text-content-primary",
 						headerClassName,
 					)}
 				>
 					{header}
 					<ChevronDownIcon
 						className={cn(
-							"h-3 w-3 shrink-0 text-content-secondary transition-transform",
+							"ml-auto h-3 w-3 shrink-0 text-current transition-transform",
 							expanded ? "rotate-0" : "-rotate-90",
 						)}
 					/>