feat(dashboard): focus same-page Start Session input from NextStep CTA and checklist

The "Start a session" CTAs on the NextStepCard and SetupChecklist used to
Link-navigate, which left the user on the same page (the Start Session
input lives on the dashboard) without any visible response. Replace those
CTAs with a custom window-event dispatch (FOCUS_START_SESSION_EVENT) that
the StartSessionInput listens for: scroll the input into view, focus the
textarea, and pulse a ring for 900ms so the click feels intentional. The
NextStepCard also locally hides itself after firing so the user isn't
double-prompted while typing.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/components/dashboard/SetupChecklist.tsx

@@ -5,6 +5,7 @@ import type { OnboardingStatus } from '@/api/onboarding'
 import { useTrialBanner } from '@/hooks/useTrialBanner'
 import type { TrialBannerStage } from '@/hooks/useTrialBanner'
 import { useOnboardingStatus } from '@/hooks/useOnboardingStatus'
+import { FOCUS_START_SESSION_EVENT } from '@/components/dashboard/StartSessionInput'
 
 /**
  * Unified setup checklist — single list (no SOLO/TEAM bifurcation).
@@ -112,6 +113,21 @@ export function SetupChecklist() {
                   {item.label}
                 </span>
               </div>
+            ) : item.key === 'ran_session' ? (
+              <button
+                type="button"
+                onClick={() => window.dispatchEvent(new Event(FOCUS_START_SESSION_EVENT))}
+                className={cn(
+                  'w-full flex items-center gap-3 rounded-lg px-3 py-2 text-sm transition-colors text-left',
+                  'hover:bg-[rgba(255,255,255,0.04)]',
+                )}
+                data-testid={`checklist-item-${item.key}`}
+                data-done="false"
+              >
+                <span className="flex h-5 w-5 shrink-0 items-center justify-center rounded-md border border-border" />
+                <span className="flex-1 text-foreground">{item.label}</span>
+                <ChevronRight size={14} className="text-muted-foreground shrink-0" />
+              </button>
             ) : (
               <Link
                 to={item.path}