P0-3a: dedupe the Explore leaderboard — one row per player+market + per-market cap

Phone audit: leaderboard flooded with 9 consecutive identical 'stolen_bases U0.5
45% B' rows. New shared lib/playerGrouping (dedupeLeaders + groupIntoLadders,
name-key aware, 7 unit tests): ONE row per (player, market family) keeping the
best-ranked, then a per-market cap (4) so no single prop type floods the board.
Applied to ExploreHub. Ledger cards + Consensus grouping follow in P0-3b/c using
the same lib.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/components/ExploreHub.tsx

@@ -4,6 +4,7 @@ import { useEffect, useMemo, useState } from 'react';
 import SportBadge from '@/components/vyndr/SportBadge';
 import GradeBadge from '@/components/vyndr/GradeBadge';
 import { playerHref } from '@/lib/playerHref';
+import { dedupeLeaders } from '@/lib/playerGrouping';
 
 /**
  * ExploreHub (Session 42 leaders; Session 60 night2/C — THE AGGREGATOR).
@@ -54,7 +55,11 @@ export default function ExploreHub() {
 
   const rows = useMemo(() => {
     const q = query.trim().toLowerCase();
-    return q ? leaders.filter((l) => (l.player || '').toLowerCase().includes(q)) : leaders;
+    const filtered = q ? leaders.filter((l) => (l.player || '').toLowerCase().includes(q)) : leaders;
+    // P0-3 — ONE row per player+market family + a per-market cap, so a player's
+    // alt-line ladder (Bohm ×3) collapses to one entry and no single prop type
+    // (9× stolen_bases) can flood the ranked board.
+    return dedupeLeaders(filtered, 4) as Leader[];
   }, [leaders, query]);
 
   // Wave 2B — never-dark hub. When the selected sport is in its OFF-SEASON, the