chore: add render-error test button to sidebar

Add a second temporary PostHog validation button that throws during render
(caught by the error boundary → posthog.captureException), alongside the
existing handler-throw button (caught by capture_exceptions).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: huv1k

src/features/dashboard/sidebar/footer.tsx

@@ -24,7 +24,10 @@ import {
 } from '@/ui/primitives/sidebar'
 import DashboardSurveyPopover from '../navbar/dashboard-survey-popover'
 import ContactSupportDialog from '../navbar/report-issue-dialog'
-import { ThrowErrorTestButton } from './throw-error-test-button'
+import {
+  RenderErrorTestButton,
+  ThrowErrorTestButton,
+} from './throw-error-test-button'
 
 export default function DashboardSidebarFooter() {
   return (
@@ -34,6 +37,7 @@ export default function DashboardSidebarFooter() {
           <SidebarMenu>
             {/* TEMPORARY: PostHog error-tracking validation (ENG-4261). Remove later. */}
             <ThrowErrorTestButton />
+            <RenderErrorTestButton />
             <SidebarMenuItem key="github">
               <SidebarMenuButton asChild tooltip="GitHub">
                 <Link

src/features/dashboard/sidebar/throw-error-test-button.tsx

@@ -1,5 +1,6 @@
 'use client'
 
+import { useState } from 'react'
 import { BugIcon } from '@/ui/primitives/icons'
 import { SidebarMenuButton, SidebarMenuItem } from '@/ui/primitives/sidebar'
 
@@ -28,3 +29,33 @@ export function ThrowErrorTestButton() {
     </SidebarMenuItem>
   )
 }
+
+/**
+ * TEMPORARY — validates PostHog error tracking end-to-end (ENG-4261).
+ *
+ * Clicking flips state so the component throws on its next render. A render
+ * error is caught by the nearest error boundary (error.tsx → the shared
+ * ErrorBoundary), which reports it via posthog.captureException. This exercises
+ * the boundary path, as opposed to ThrowErrorTestButton's uncaught-handler path.
+ *
+ * Remove this component (and its usage in the sidebar footer) once verified.
+ */
+export function RenderErrorTestButton() {
+  const [shouldThrow, setShouldThrow] = useState(false)
+
+  if (shouldThrow) {
+    throw new Error('PostHog error tracking test — thrown during render')
+  }
+
+  return (
+    <SidebarMenuItem key="render-error-test">
+      <SidebarMenuButton
+        tooltip="Throw render error"
+        onClick={() => setShouldThrow(true)}
+      >
+        <BugIcon />
+        Throw render error
+      </SidebarMenuButton>
+    </SidebarMenuItem>
+  )
+}