P1-7: flat edge board — guard the broken edge placeholder (absent > fabricated)

Phone audit called the board 'mostly-empty'. Two causes, both now addressed:
1. Dead images (P0-2, already fixed) → the matchup/team chips render logos now.
2. Degraded edge data. Live snapshot edge_pct is on a broken scale (distinct
   values 20/60/100/140 — not a market %), with projection=0 and confidence
   35-55%. A real prop-market edge is single-digit, never past ~40%. Leading
   the board with '+140%' fabricates a signal (Data Semantics Rule).

Fix: an edge whose |value| > 40 is treated as ABSENT at BOTH layers — the
data layer (flattenToEdgeBoard nulls it, so it can't RANK a fake +140% above a
real +8.4%) and the display (EdgeCell shows '—'). Board falls through to the
grade-rank tiebreak when edges are unreliable. Real edges (≤40) are untouched.

The root cause — edge_pct/projection/confidence degradation — is a BACKEND
grading issue (same family as the P2-9 '45% B' flag), reported separately; this
is the honest frontend guard, not a fix for the data.

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

web/src/lib/slateAdapter.js

@@ -608,6 +608,10 @@ const EDGE_GRADE_RANK = { 'A+': 0, A: 1, 'A-': 2, 'B+': 3, B: 4, 'B-': 5, C: 6,
 function edgeGradeRank(g) {
   return EDGE_GRADE_RANK[g] != null ? EDGE_GRADE_RANK[g] : 9;
 }
+// Ceiling for a plausible prop-market edge; beyond it the value is a broken
+// placeholder, not a signal (mirrored in MobileEdgeBoard.EdgeCell).
+const EDGE_BOARD_SANE_MAX = 40;
+
 function flattenToEdgeBoard(cards) {
   const rows = [];
   for (const c of Array.isArray(cards) ? cards : []) {
@@ -624,7 +628,11 @@ function flattenToEdgeBoard(cards) {
           line: p.line,
           side: p.side || 'O',
           grade: p.grade,
-          edge: (p.edge != null && Number.isFinite(p.edge)) ? p.edge : null,
+          // A real prop edge is single-digit %, never past ~40. Values beyond
+          // that are the pipeline's miscalibrated placeholder (live: 60/100/140)
+          // — treat as absent so the board neither displays nor RANKS on a fake
+          // edge. When absent, rows fall through to the grade-rank tiebreak.
+          edge: (p.edge != null && Number.isFinite(p.edge) && Math.abs(p.edge) <= EDGE_BOARD_SANE_MAX) ? p.edge : null,
           sport: c.sport || '',
           away,
           home,