Item 6 — Desk showcase renders REAL data (or hides), kills the mocked ladder

The pricing Desk showcase hardcoded an alt-line ladder (1.5 A +7.1% / 2.5 A+
+11.4% / 4.5 C -3.8%), QUARTER-KELLY 2.4%, and PARLAY φ 0.34 — a mocked demo
selling something we weren't proving.

- deskShowcaseService reads the pre-graded snapshot for a real A/B prop's
  alt-line ladder (prefers the one with the most grade variation — the most
  compelling real example). Edge per rung shows only when it's a plausible
  market value; the inflated (model-line)/line artifact on small lines is
  guarded to "—" rather than shown as a fake +91%.
- PARLAY φ is now REAL: the model's same-team correlation (0.34, mirroring the
  frontend parlayMath team constant) computed for TWO REAL same-team legs,
  named. No real same-team pair on the board → the tile hides, never an
  invented number.
- QUARTER-KELLY tile is REMOVED: the snapshot has no odds, so a real
  quarter-Kelly % can't be computed here — a fabricated 2.4% is worse than
  nothing. Kelly stays a real in-app Desk feature; the showcase just doesn't
  fake it.
- DeskShowcase is now a client component fetching /api/desk-showcase; when the
  board has no real ladder the whole visuals column hides (real-or-hidden, same
  law as the hero). The pitch copy is unchanged.

5 service tests. Change-affected suites green, web build exit 0.

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

src/app.js

@@ -217,6 +217,7 @@ app.use('/api/internal', internalRoutes);
 app.use('/api/partners', require('./routes/partners'));
 app.use('/api/founders', require('./routes/founders'));
 app.use('/api/hero-prop', require('./routes/heroProp'));
+app.use('/api/desk-showcase', require('./routes/deskShowcase'));
 
 // Session 10 — Sentry's Express error handler catches uncaught
 // errors from every route mounted above. Must come AFTER routes but