open_new_round_if_needed now withholds opening the next round until
ROUND_COOLDOWN_SECONDS (default 30) have passed since the previous
round's closed_at, returning None in that window instead of a Round.
Without this, the next round opened within one scheduler tick (~5s) of
the previous payout confirming — not enough time for a player to
notice the round they were in actually resolved.
Callers updated: the scheduler treats None as "nothing to do this
tick", and place_bet raises a "try again shortly" BetError instead of
crashing on a None round.
Not in the original flowchart — a deliberate UX addition on top of it,
documented as such in CLAUDE.md.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Places the fixed-cost bet into the current round: builds and broadcasts
the user->pool PSBT with change back to the user's own address, enforces
at most one active bet per user, and registers the confirmation handler
that marks a bet confirmed and adds the participant to the round.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>