Opening a compare link while localStorage held a different basket raced a
fetch for the OLD school set against the URL's SSR data; the stale
response replaced comparisonData, so no active school had data and every
section (including the trends chart) vanished until a hard refresh.
Responses from superseded effect runs are now dropped, successful ones
merge instead of replace, and the URL-seed effect re-runs when a
client-side navigation changes ?urns=.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0146VHeLAWjDVE2B5uU67jCB
