Merge DS4 (design): billboards — STREAKS row, grade reveal, CLV reframe, /u profile

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

# Conflicts:
#	web/src/app/ledger/page.tsx

web/src/lib/clvDisplay.js

@@ -0,0 +1,45 @@
+/**
+ * clvDisplay (DS4 · Billboards — CLV reframe, DESIGN-SPEC Part 3 #16).
+ *
+ * "Charts that are flat should SAY so." When settled CLV is near-flat (e.g.
+ * 73 of 74 reads landed at the close), a 7-bar histogram is one giant bar and
+ * six empty stubs — it reads as BROKEN. The record (55-19, 74% hit) is the
+ * best data on the site; it must look the MOST premium, never errored.
+ *
+ * This is the single pure decision: given the server's `clv_distribution`
+ * (already n≥20 gated in ledgerService), decide FLAT vs SPREAD. Flat → a
+ * confident VOICE line. Spread → the real bars. Pure + CommonJS so the .tsx
+ * consumers (ledger, profile) and Jest share one tested rule.
+ */
+
+// The flat bucket must hold this share of settled CLV for the histogram to be
+// declared "flat." 73/74 → 0.986; a genuinely dispersed book → well under.
+const FLAT_SHARE_THRESHOLD = 0.6;
+
+// VOICE-compliant one-liner. No jargon; states the model's actual claim.
+const CLV_FLAT_LINE = 'CLV flat — we grade the outcome, not the close.';
+
+/**
+ * @param {Array<{label:string,count:number,side:'beat'|'faded'|'flat'}>|null} dist
+ * @returns {{ mode:'flat'|'spread'|'none', total:number, flat:number, flatShare:number }}
+ */
+function clvMode(dist) {
+  if (!Array.isArray(dist) || dist.length === 0) {
+    return { mode: 'none', total: 0, flat: 0, flatShare: 0 };
+  }
+  const total = dist.reduce((n, b) => n + (Number(b && b.count) || 0), 0);
+  if (total <= 0) return { mode: 'none', total: 0, flat: 0, flatShare: 0 };
+  const flat = dist
+    .filter((b) => b && b.side === 'flat')
+    .reduce((n, b) => n + (Number(b.count) || 0), 0);
+  const flatShare = flat / total;
+  const mode = flatShare >= FLAT_SHARE_THRESHOLD ? 'flat' : 'spread';
+  return { mode, total, flat, flatShare };
+}
+
+/** Convenience predicate for the flat branch. */
+function isFlatClv(dist) {
+  return clvMode(dist).mode === 'flat';
+}
+
+module.exports = { clvMode, isFlatClv, CLV_FLAT_LINE, FLAT_SHARE_THRESHOLD };