Function findMostRecentBackup

src/utils/config.ts:1380–1427

* Find the most recent backup file for a given config file. * Checks ~/.claude/backups/ first, then falls back to the legacy location * (next to the config file) for backwards compatibility. * Returns the full path to the most recent backup, or null if none exist.

(file: string)

 * Returns the full path to the most recent backup, or null if none exist.
 */
function findMostRecentBackup(file: string): string | null {
  const fs = getFsImplementation()
  const fileBase = basename(file)
  const backupDir = getConfigBackupDir()

  // Check the new backup directory first
  try {
    const backups = fs
      .readdirStringSync(backupDir)
      .filter(f => f.startsWith(`${fileBase}.backup.`))
      .sort()

    const mostRecent = backups.at(-1) // Timestamps sort lexicographically
    if (mostRecent) {
      return join(backupDir, mostRecent)
    }
  } catch {
    // Backup dir doesn't exist yet
  }

  // Fall back to legacy location (next to the config file)
  const fileDir = dirname(file)

  try {
    const backups = fs
      .readdirStringSync(fileDir)
      .filter(f => f.startsWith(`${fileBase}.backup.`))
      .sort()

    const mostRecent = backups.at(-1) // Timestamps sort lexicographically
    if (mostRecent) {
      return join(fileDir, mostRecent)
    }

    // Check for legacy backup file (no timestamp)
    const legacyBackup = `${file}.backup`
    try {
      fs.statSync(legacyBackup)
      return legacyBackup
    } catch {
      // Legacy backup doesn't exist
    }
  } catch {
    // Ignore errors reading directory
  }

  return null
}

function getConfig<A>(
  file: string,