subscribeVideos now goes through the L1 SubscriptionManager instead of calling
pool.sub directly: health-gated relay resolution (healthy-or-default fallback
preserved), centralized dedup, and registration for reconnect re-issue. The
buffer + .unsub() contract are unchanged. The client's manager uses its own
RelaySubscriptionService instance (isolated from the global singleton).
Verified: subscribeVideos relay-fallback + client + nostr-service suites pass;
ux-harness renders the grid (first card ~1.1s); steady-state REQ/ext idle.
(Pre-existing nostr-delete-flow failure confirmed unrelated — fails at the
pre-session baseline too.)
Co-Authored-By: Claude Opus 4.8 <[email protected]>
