Fix double elimination with byes never finishing; hand-built brackets

Byes now cascade through the whole bracket (a slot nobody can fill is a bye or
a void), re-run on server start so stuck tournaments recover. New manual
bracket builder on the desk: pick round-1 pairings per match. Tests at 5-23
teams for both bracket types. Release 0.5.0.

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01MB7nCCAscYsb3zzkT6LHZi

docs/KNOWN-GAPS.md

@@ -4,7 +4,6 @@ Honest list of what the MVP does not do well yet. None of these block running a
 
 - **No real-event mileage yet.** The engine has been exercised by `simulate.js` (dozens of seeds, single and double elimination) and the HTTP smoke test, and the pages have been eyeballed on phone and desktop sizes. It has not run an actual tournament.
 - **Bracket corrections don't re-propagate.** Correcting a bracket match after its winner has already played the next round does not rewind the later match; you must correct that one too. Pool corrections are fine (standings are recomputed).
-- **Double elimination with byes** is tested at 6 teams (8-bracket). Very uneven fields (9–10 teams in a 16-bracket) get the same bye logic but have had less scrutiny.
 - **Queue priority is round-first.** A round-2 match between two rested teams waits behind a round-1 match whose teams just came off court. That keeps pools fair (everyone plays round N before anyone plays round N+1) but can leave a court briefly idle. The engine is a single function (`_eligible`) if you want a different policy.
 - **ETAs are estimates.** They come from the rolling average of the last six matches and assume a fixed changeover. Early in the day (fewer than one finished match) the default is 15 minutes.
 - **Alerts are on-page only.** A team must have their team page open (or the notification permission granted) to be alerted. SMS and Web Push are the top roadmap items.