S3 (a1): affiliate + partner plumbing

Zero out-of-pocket; everything config-flip-ready but DISABLED/organic.

- BOOK IT deep links: web/src/lib/bookLinks.js + affiliateConfig.js
  (all books enabled:false, Impact/Partnerize param shapes documented,
  empty params skipped). Wired into StatStrip BookItTeaser (real anchor
  now) + scan hand-off links. Every book anchor renders
  rel="sponsored noopener noreferrer" (BOOK_LINK_REL).
- Best-price marker: slateAdapter.detectBestBook (only when >=2 books
  post the SAME line and prices differ — absent beats wrong) + subtle
  signal-green dot in StatStrip. Slate.groupByGame threads the grouped
  per-book rows (books[]) onto PropRowProp instead of discarding them.
- Partner refs: ?ref=CODE -> vyndr_ref cookie (90d, first-touch,
  PartnerRefCapture in layout) -> signup metadata partner_ref ->
  internal GET /api/partners/report/:code (requireInternalAuth; honest
  zeros + note until the TODO migration in docs/PARTNERS.md adds
  user_profiles.partner_ref — NOT run). Stripe promo-code convention:
  partner code == promotion code, verbatim.
- Tests: +41 (2398 -> 2439, 209 suites); bookItTeaser + vyndrCoreScreens
  invariants updated to the new (stronger) rel contract. Web build exit 0.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

BUILD-STATE.md

@@ -1,7 +1,24 @@
 # VYNDR — Build State
 
 ## Last Updated
-2026-07-10
+2026-07-11
+
+## Session S3 (a1 board, 2026-07-11) — Affiliate + Partnership Plumbing ✅
+Zero out-of-pocket; everything config-flip-ready but DISABLED/organic.
+2398 → **2439 tests** (209 suites), web build exit 0.
+- **BOOK IT deep links** — `web/src/lib/bookLinks.js` + `affiliateConfig.js`
+  (every book `enabled:false`; Impact/Partnerize param shapes documented).
+  StatStrip BOOK IT is a real anchor now (organic); scan hand-off links moved
+  to the builder. Every book anchor renders `rel="sponsored noopener noreferrer"`.
+- **Best-price marker** — `slateAdapter.detectBestBook` (≥2 books, SAME line,
+  differing prices, else null) + green dot in StatStrip; `books[]` (the grouped
+  odds rows) now threads Slate → strips instead of being discarded by pickLine.
+- **Partner refs** — `?ref=CODE` → 90d first-party `vyndr_ref` cookie
+  (first-touch, `PartnerRefCapture` in layout) → signup metadata `partner_ref`
+  → internal `GET /api/partners/report/:code` (zeros + note until the TODO
+  migration in docs/PARTNERS.md adds `user_profiles.partner_ref`; NOT run).
+- **docs/PARTNERS.md** — ref link spec, Stripe promo-code mapping convention
+  (partner code == promotion code), TODO migration SQL.
 
 ## Current Phase
 SHIP BUILD v59.0 — Overnight session: ledger team/opponent addendum,