Richer event context: buildup lines from the full play-by-play feed

'X is shown a red card' alone isn't insight — the story is in the
surrounding plays. The ESPN summary carries a ~110-line play-by-play
feed (attempts, fouls, corners, VAR checks) we cached but never used:

- normalizer keeps a trimmed commentary list (schema v3; the boot
  backfill re-stores older matches automatically)
- previews serve it; expanding a timeline event now shows up to four
  feed lines from the three minutes leading in, then the event's own
  description — e.g. Korea's saved attempt and corner right before
  Czechia's counter-goal header, or the foul behind a booking

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

src/lib/matchEvents.ts

@@ -145,6 +145,35 @@ export function eventContext(e: ParsedEvent): string | null {
   return ctx;
 }
 
+export interface CommentaryLine { minute: number | null; text: string }
+
+/**
+ * The feed lines leading into an event — the buildup story shown when a
+ * timeline item is expanded (the saved attempt before a counter-goal, the
+ * foul before a card, a VAR check). Anchored on the entry that IS the event
+ * (same text), else the last entry at the event's minute; returns up to
+ * `max` preceding lines no older than three minutes.
+ */
+export function buildup(e: ParsedEvent, commentary: CommentaryLine[], max = 4): CommentaryLine[] {
+  if (e.minute == null || !commentary.length) return [];
+  let anchor = commentary.findIndex((c) => c.text === e.raw);
+  if (anchor === -1) {
+    for (let i = 0; i < commentary.length; i++) {
+      const m = commentary[i]!.minute;
+      if (m != null && m <= e.minute) anchor = i;
+      if (m != null && m > e.minute) break;
+    }
+  }
+  if (anchor <= 0) return [];
+  const out: CommentaryLine[] = [];
+  for (let i = anchor - 1; i >= 0 && out.length < max; i--) {
+    const c = commentary[i]!;
+    if (c.minute == null || c.minute < e.minute - 3) break;
+    out.unshift(c);
+  }
+  return out;
+}
+
 /** Score at half-time: last goal score at minute ≤ 45 (0–0 when none). */
 export function halfTimeScore(parsed: ParsedEvent[]): [number, number] {
   let ht: [number, number] = [0, 0];