fix(ui-trajectory): clarify collapsed thinking controls

packages/client/ui-trajectory/src/client/TrajectoryTable.module.css

@@ -1248,9 +1248,19 @@
   background: transparent;
   cursor: pointer;
   font: 600 12px/18px var(--dsw-font-family);
+  gap: 2px;
   user-select: none;
 }
 
+.thinkingChevron {
+  flex: none;
+  transition: transform 120ms var(--ds-ease-in-out);
+}
+
+.thinkingToggle[aria-expanded='true'] .thinkingChevron {
+  transform: rotate(90deg);
+}
+
 .thinkingToggle:hover {
   color: var(--dsw-alias-label-secondary);
 }

packages/client/ui-trajectory/src/client/TrajectoryTable.tsx

@@ -1232,7 +1232,8 @@ function MarkdownRecordContent({
             aria-expanded={thinkingExpanded}
             onClick={() => { onThinkingExpandedChange(!thinkingExpanded) }}
           >
-            {thinkingExpanded ? 'Thinking' : 'Thinking ...'}
+            {thinkingExpanded ? 'Hide thinking' : 'Show thinking'}
+            <IconChevronRightOutline14 className={css.thinkingChevron} size={12} />
           </button>
           {thinkingExpanded && (
             <MarkdownFragment

packages/client/ui-trajectory/tests/table.spec.tsx

@@ -101,10 +101,13 @@ describe('TrajectoryTable', () => {
     render(<TrajectoryTable turns={turns} {...FOLD_PROPS} />)
 
     fireEvent.click(screen.getByRole('row', { name: /ASSISTANT/ }))
-    const toggle = screen.getByRole('button', { name: 'Thinking ...' })
+    const toggle = screen.getByRole('button', { name: 'Show thinking' })
+    expect(toggle.getAttribute('aria-expanded')).toBe('false')
     expect(screen.queryByText(thinking)).toBeNull()
 
     fireEvent.click(toggle)
+    expect(screen.getByRole('button', { name: 'Hide thinking' })).toBe(toggle)
+    expect(toggle.getAttribute('aria-expanded')).toBe('true')
     expect(toggle.parentElement?.textContent?.length).toBeGreaterThan(thinking.length)
   })