Optional. Case-insensitive prefix match against both username and address.

Optional sort column: rank | trading_score | volume_score | pnl_score |
roi_percent | win_rate | realized_pnl. Empty keeps the track's own ordering.
This re-sorts the board as a table; it does not change which track is being
read. realized_pnl and roi_percent disagree whenever traders started from
different capital.

Optional sort direction: asc | desc. Empty uses the column's natural
best-first order (ascending for rank, descending for scores). Ignored when
sort_by is empty.

Optional reward track: empty for the competition's primary track, otherwise
one of the tracks its scoring_config lists (roi | volume | oi). This is the
page's track toggle. It selects both the board's ordering and the gate set
behind each row's qualified, since a wallet holds a different position and
can hold different eligibility in each track. Rejected when the competition
does not offer the named track.

A competition can be presented as two peer tracks with no primary between
them — Double Top pays volume share and time-weighted OI share from separate
pools — in which case every read names the track it means.