- Wrap CooldownFrame._SetCooldown secret arithmetic in pcall
  function (addon code cannot do secret - secret, unlike Blizzard
  trusted code). Falls back to static colored border if arithmetic
  fails.
- Guard sort comparator against nil cache entries to prevent
  crash when auraInstanceID is in _debuffs_raid but not in cache.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>