Withdrawn teams forfeit visibly through the bracket instead of becoming byes

A withdrawn team stays in any slot whose opponent is not known yet and forfeits
when they arrive; the board strikes the name through and tags the match
'Forfeit · Team'. Release 0.5.1.

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

docs/ORGANIZER-GUIDE.md

@@ -46,7 +46,7 @@ A keeper link can only do two things: update the running score of the live match
 - *forfeit remaining* — their unplayed pool games become forfeit wins for the opponents; played games stand. This is the fair default when a team leaves mid-pool.
 - *void all games* — every game they played or would play is removed from standings, as if they never entered. Use this when a team leaves early and forfeits would distort the pool.
 
-In a bracket the opponent advances automatically either way.
+In a bracket the opponent advances by forfeit either way: the bracket shows the withdrawn team struck through with a "Forfeit" tag on each match it was in, including a later match whose opponent wasn't known yet at the time (it forfeits as soon as that opponent arrives). Play carries on and the tournament still finishes on its own.
 
 **Rain, injury, net repair.** Pause the court (with an optional reason shown on the board). The queue keeps flowing to the other court; Resume picks up where it left off.