FN-6339: combine consecutive thinking entries

Render grouped task-chat thinking logs as one continuous section.

- Concatenate grouped thinking entry text before markdown rendering.
- Keep the thinking disclosure summary stable as "Thinking" instead of showing entry counts.
- Move spacing to tool groups and remove multi-thinking divider styling.
- Cover the combined thinking rendering behavior in TaskChatTab tests.

Files changed:
 packages/dashboard/app/components/TaskChatTab.css  | 10 ++++-----
 packages/dashboard/app/components/TaskChatTab.tsx  | 25 ++++++++++------------
 .../app/components/__tests__/TaskChatTab.test.tsx  | 23 +++++++++++++++++++-
 3 files changed, 37 insertions(+), 21 deletions(-)

Fusion-Task-Id: FN-6339

Fusion-Task-Lineage: 51a2ea27-a56a-4844-a27b-389d1d24613f

packages/dashboard/app/components/TaskChatTab.css

@@ -147,10 +147,13 @@
 .task-chat-thinking-body {
   display: flex;
   flex-direction: column;
-  gap: var(--space-sm);
   padding: 0 var(--space-md) var(--space-md);
 }
 
+.task-chat-tool-group-entries {
+  gap: var(--space-sm);
+}
+
 .task-chat-tool-entry {
   min-width: 0;
   padding: var(--space-sm) var(--space-md);
@@ -176,11 +179,6 @@
   font-weight: 600;
 }
 
-.task-chat-thinking-markdown + .task-chat-thinking-markdown {
-  padding-top: var(--space-sm);
-  border-top: var(--btn-border-width) solid color-mix(in srgb, var(--color-warning) 24%, var(--border));
-}
-
 .task-chat-entry-kicker {
   margin-bottom: var(--space-xs);
   color: var(--text-muted);

packages/dashboard/app/components/TaskChatTab.tsx

@@ -301,23 +301,20 @@ function TaskChatToolGroup({ entries }: { entries: AgentLogEntry[] }) {
 }
 
 function TaskChatThinking({ entries }: { entries: AgentLogEntry[] }) {
+  const combinedThinkingText = entries.map((entry) => entry.text).join("");
+
   return (
     <details className="task-chat-thinking" data-testid="task-chat-thinking" open>
-      <summary className="task-chat-thinking-summary">
-        {entries.length === 1 ? "Thinking" : `${entries.length} thinking entries`}
-      </summary>
+      <summary className="task-chat-thinking-summary">Thinking</summary>
       <div className="task-chat-thinking-body">
-        {entries.map((entry, entryIndex) => (
-          <div
-            className="markdown-body task-chat-markdown task-chat-thinking-markdown"
-            data-testid="task-chat-entry-thinking"
-            key={getEntryKey(entry, entryIndex)}
-          >
-            <ReactMarkdown remarkPlugins={[remarkGfm]} components={markdownComponents}>
-              {entry.text}
-            </ReactMarkdown>
-          </div>
-        ))}
+        <div
+          className="markdown-body task-chat-markdown task-chat-thinking-markdown"
+          data-testid="task-chat-entry-thinking"
+        >
+          <ReactMarkdown remarkPlugins={[remarkGfm]} components={markdownComponents}>
+            {combinedThinkingText}
+          </ReactMarkdown>
+        </div>
       </div>
     </details>
   );

packages/dashboard/app/components/__tests__/TaskChatTab.test.tsx

@@ -377,8 +377,9 @@ describe("TaskChatTab", () => {
 
     const thinking = screen.getByTestId("task-chat-thinking");
     expect(thinking).toHaveAttribute("open");
-    expect(screen.getByText("Thinking")).toBeVisible();
+    expect(within(thinking).getByText("Thinking")).toBeVisible();
     expect(screen.getByText("I am considering options")).toBeVisible();
+    expect(within(thinking).getAllByTestId("task-chat-entry-thinking")).toHaveLength(1);
 
     await user.click(within(thinking).getByText("Thinking"));
 
@@ -386,6 +387,25 @@ describe("TaskChatTab", () => {
     expect(screen.getByText("I am considering options")).not.toBeVisible();
   });
 
+  it("renders consecutive thinking entries as one continuous section", () => {
+    mockLogs([
+      makeEntry({ agent: "triage", type: "thinking", text: "First" }),
+      makeEntry({ agent: "triage", type: "thinking", text: "Second", timestamp: "2026-06-12T00:00:01.000Z" }),
+    ]);
+
+    render(<TaskChatTab task={makeTask()} active addToast={vi.fn()} />);
+
+    const thinking = screen.getByTestId("task-chat-thinking");
+    const summary = thinking.querySelector("summary");
+    expect(summary).toBeTruthy();
+    expect(within(summary as HTMLElement).getByText("Thinking")).toBeVisible();
+    expect(screen.queryByText("2 thinking entries")).not.toBeInTheDocument();
+    const thinkingBlocks = within(thinking).getAllByTestId("task-chat-entry-thinking");
+    expect(thinkingBlocks).toHaveLength(1);
+    expect(thinkingBlocks[0]).toHaveTextContent("FirstSecond");
+    expect(thinkingBlocks[0].nextElementSibling).toBeNull();
+  });
+
   it("creates distinct tool segments when text or thinking entries are interleaved", () => {
     mockLogs([
       makeEntry({ agent: "executor", type: "tool", text: "first tool", detail: "first detail" }),
@@ -820,5 +840,6 @@ describe("TaskChatTab", () => {
     expect(css).toContain(".task-chat-tool-group-names");
     expect(css).toContain(".task-chat-tool-group-error-count");
     expect(css).toContain(".task-chat-thinking-summary");
+    expect(css).not.toContain(".task-chat-thinking-markdown + .task-chat-thinking-markdown");
   });
 });