Function findLatestMessage

src/utils/sessionStorage.ts:2047–2062

* O(n) single-pass: find the message with the latest timestamp matching a predicate. * Replaces the `[...values].filter(pred).sort((a,b) => Date(b)-Date(a))[0]` pattern * which is O(n log n) + 2n Date allocations.

(
  messages: Iterable<T>,
  predicate: (m: T) => boolean,
)

 * which is O(n log n) + 2n Date allocations.
 */
function findLatestMessage<T extends { timestamp: string }>(
  messages: Iterable<T>,
  predicate: (m: T) => boolean,
): T | undefined {
  let latest: T | undefined
  let maxTime = -Infinity
  for (const m of messages) {
    if (!predicate(m)) continue
    const t = Date.parse(m.timestamp)
    if (t > maxTime) {
      maxTime = t
      latest = m
    }
  }
  return latest
}

/**
 * Builds a conversation chain from a leaf message to root