Each chat message is a shielded tx that spends a verified note, so a burst of
messages hit "insufficient verified funds" once the single note is spent. Add a
per-frame note-buffer coordinator (both variants) that keeps ~10 verified
spendable notes: it serializes sends through the one broadcast channel, counts
verified notes by block depth (lite) or a rate-limited z_listunspent scan
(full node), self-splits in the background to refill toward the target, and
queues overflow to drain as change matures — with honest Sent/Failed status
instead of the prior optimistic "Sent". Guardrails: single split in flight with
a watchdog, cooldown, and session-generation guards so a wallet switch can't
drain another wallet's queue. Surface a "Chat buffer: N/10 ready" indicator in
the status bar while the Chat tab is active, and route chat diagnostics through
the console on both variants (the full-node console now drains the shared ring).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>