performProfileFetch now issues ONE deduped, health-gated list() across all
relays via the L1 SubscriptionManager (the pool merges per-relay results),
replacing the manual per-relay fan-out. Newest-per-author selection unchanged;
legacy per-relay path retained as the manager-less fallback.
Spec correction: tests/app-batch-fetch-profiles.test.mjs asserted one query
PER relay (implementation detail); updated to assert one BATCHED query across
all relays. All behavioral assertions (cached hydration, newest profile
rendered, failing relay tolerated) unchanged; added a relays-targeting
assertion. Documented in TEST_INTEGRITY.md (SCN-profiles-batched).
Co-Authored-By: Claude Opus 4.8 <[email protected]>
