D1 finish: row-hover rationale, IntersectionObserver reveal, team-gradient chips

Additive frontend. Backend untouched (git diff src/ = empty): no grade, model,
classifier or ledger change. Scope held to the row anatomy these three items
need — no System-artboard-wide rebuild. Push scoring untouched.

REVIEW ZERO — the two checks that decided whether these could be honest:

0.2 RATIONALE SOURCE — VERIFIED REAL. Live snapshot grades carry `reasoning`
    and `kill_conditions_triggered`. The summary is built by analyzeViaEngine1
    from the actual feature vector (l5/l20 averages, gap to the line, home/away,
    opponent defensive rank, rest days) and kills carry real codes + reasons.
    So the hover shows genuine grade truth, not a placeholder.

0.3 TEAM COLOURS — PARTIAL, and deliberately left partial. The System artboard
    defines a colour pair for only 10 teams (BOS CHC CHI DEN LAD MIL MIN NYY PIT
    SD), lifted verbatim; lib/teams.js holds ~80. The other ~70 are NOT invented
    — a wrong team colour is a recognition error the user reads as fact. Unknown
    teams get the honest-neutral chip (muted border, no colour claim), never a
    guess and never a blank gap. Coverage is reported by coverage(), not hidden.

SHIPPED:
- web/src/lib/rowRationale.js — rationaleFor() returns real summary + kills, or
  NULL. No generic fallback: an empty hover is honest, a manufactured "why" is a
  fabricated model explanation. A locked/tier-gated reasoning is treated as
  ABSENT rather than paraphrased or leaked, and a kill condition with no reason
  explains nothing so it is dropped.
- web/src/lib/reveal.js — IntersectionObserver reveal that fires ONCE then
  unobserves ("react to truth, then rest"), reuses D1-A's bootDelayMs for the
  60ms stagger so there is ONE source of truth for the timing, and reveals
  IMMEDIATELY when IntersectionObserver is absent (SSR/test) so a missing API can
  never hide real content. Reduced motion is handled by the existing CSS, so the
  row is visible either way.
- web/src/lib/teamChips.js — Rev-3 geometry (10px, 135deg, before the abbr,
  inside the row) plus the ranked opacity ramp 1/.86/.64/.48 so chips dim with
  their row. Swap-ready for licensed logos at the same size.

Floor: 318 suites / 3961 tests green (15 new), web build exit 0.

The three modules are pure and unit-locked; mounting them into the live row
components is a follow-up, and the visual result belongs in the Chrome audit.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QJs13VsyiSKYQP6rj3NNmc

web/src/lib/teamChips.js

@@ -0,0 +1,68 @@
+'use strict';
+/**
+ * TEAM-GRADIENT CHIPS (D1-finish, 2026-07-31) — Rev-3 pattern from HANDOFF.md:
+ *   10-12px chip, 135deg two-colour gradient, placed BEFORE each team abbr and
+ *   INSIDE the row, so the ranked opacity ramp (1 / .86 / .64 / .48) dims it too.
+ *   Swap for a licensed logo <img> at the same size when assets land.
+ *
+ * 🔴 COVERAGE IS PARTIAL AND THAT IS DELIBERATE. The System artboard defines a
+ * colour pair for only 10 teams; the registry (`lib/teams.js`) holds ~80. We do
+ * NOT invent the other ~70 — a wrong team colour is a recognition error the user
+ * reads as fact. Unknown teams render the HONEST-NEUTRAL chip (a muted border,
+ * no colour claim), never a guessed hue and never a blank gap.
+ *
+ * Pairs below are lifted VERBATIM from `Vyndr System.dc.html` — no eyedropping,
+ * no approximation.
+ */
+
+/** abbr -> [c1, c2], exactly as the artboard defines them. */
+const TEAM_GRADIENTS = Object.freeze({
+  BOS: ['#BD3039', '#6b1c22'],
+  CHC: ['#0E3386', '#CC3433'],
+  CHI: ['#CE1141', '#6d0a22'],
+  DEN: ['#0E4DA4', '#4C8BF5'],
+  LAD: ['#005A9C', '#2f7fd0'],
+  MIL: ['#00471B', '#0a7a3a'],
+  MIN: ['#0C2340', '#236192'],
+  NYY: ['#1b3a6b', '#0C2340'],
+  PIT: ['#2b2b2b', '#c9a227'],
+  SD:  ['#2F241D', '#8a6d4a'],
+});
+
+/** The ranked opacity ramp — chips sit inside rows so they dim with the row. */
+const RANK_OPACITY = Object.freeze([1, 0.86, 0.64, 0.48]);
+
+/** Opacity for rank index i (clamped to the ramp's tail). */
+function rankOpacity(i) {
+  const n = Number(i);
+  if (!Number.isFinite(n) || n < 0) return RANK_OPACITY[0];
+  return RANK_OPACITY[Math.min(Math.floor(n), RANK_OPACITY.length - 1)];
+}
+
+/**
+ * chipStyle(abbr) — inline style for the chip, or the honest-neutral style when
+ * the team has no designed colour. Returns `{ style, known }` so a caller can
+ * tell "we know this team" from "we are not claiming to".
+ */
+function chipStyle(abbr) {
+  const key = String(abbr || '').trim().toUpperCase();
+  const pair = TEAM_GRADIENTS[key];
+  const base = {
+    display: 'inline-block', width: 10, height: 10, borderRadius: 3,
+    verticalAlign: -1.5, marginRight: 3,
+  };
+  if (!pair) {
+    // HONEST-NEUTRAL: a shape, not a colour claim.
+    return { known: false, style: { ...base, background: 'transparent', border: '1px solid var(--border-hi)' } };
+  }
+  return { known: true, style: { ...base, background: `linear-gradient(135deg,${pair[0]},${pair[1]})` } };
+}
+
+/** How much of the registry we actually have colours for — reported, not hidden. */
+function coverage(totalTeams) {
+  const known = Object.keys(TEAM_GRADIENTS).length;
+  const total = Number(totalTeams);
+  return { known, total: Number.isFinite(total) ? total : null };
+}
+
+module.exports = { TEAM_GRADIENTS, RANK_OPACITY, rankOpacity, chipStyle, coverage };