feat(web-ui): expose citation-corroboration badge on halachot (X11)

- db.list_halachot: aggregate corroboration_count (distinct positive sources)
  + corroboration_negative from halacha_citation_corroboration (LEFT JOIN)
- web-ui: CorroborationBadge — 'מתוקף · N ציטוטים' at ≥2 (gold), soft single
  citation, danger badge on negative treatment; native title tooltips
- shown in ExtractedHalachotSection (per-precedent) + halacha review panel

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

web-ui/src/components/precedents/corroboration-badge.tsx

@@ -0,0 +1,51 @@
+import { Scale, AlertTriangle } from "lucide-react";
+import { Badge } from "@/components/ui/badge";
+import type { Halacha } from "@/lib/api/precedent-library";
+
+/* X11 — citation corroboration signal for a halacha.
+ *
+ * Shows how many distinct later courts/committees adopted this halacha
+ * (positive treatment). ≥2 distinct positive sources = "מתוקף" (the
+ * auto-approve threshold, INV-COR4); a single citation is shown more
+ * softly. A negative treatment (distinguished/criticized/overruled) is
+ * surfaced as a warning — those never auto-approve and an overruled one
+ * is sent back to the chair gate (INV-COR2). Renders nothing when there
+ * is no citation signal at all. */
+export function CorroborationBadge({ halacha }: { halacha: Halacha }) {
+  const count = halacha.corroboration_count ?? 0;
+  const negative = halacha.corroboration_negative ?? false;
+
+  if (negative) {
+    return (
+      <Badge
+        variant="outline"
+        className="text-[0.65rem] bg-danger-bg text-danger border-danger/40"
+        title="ערכאה/ועדה מאוחרת אבחנה, מתחה ביקורת או ביטלה הלכה זו — אינה מאושרת אוטומטית בתיקוף-ציטוטים (X11)"
+      >
+        <AlertTriangle className="w-3 h-3 me-1" /> טיפול שלילי בציטוט
+      </Badge>
+    );
+  }
+
+  if (count <= 0) return null;
+
+  const corroborated = count >= 2;
+  return (
+    <Badge
+      variant="outline"
+      className={
+        corroborated
+          ? "text-[0.65rem] bg-gold-wash text-gold-deep border-gold/40 tabular-nums"
+          : "text-[0.65rem] bg-rule-soft text-ink-muted tabular-nums"
+      }
+      title={
+        corroborated
+          ? `מתוקף ע"י ${count} ערכאות/ועדות מאוחרות שאימצו הלכה זו (טיפול שיפוטי מצטבר, X11)`
+          : "ציטוט מאמת בודד — מתחת לסף התיקוף (נדרשים ≥2 מקורות בלתי-תלויים, X11)"
+      }
+    >
+      <Scale className="w-3 h-3 me-1" />
+      {corroborated ? `מתוקף · ${count} ציטוטים` : "ציטוט מאמת · 1"}
+    </Badge>
+  );
+}