ReclaimDeletions ran an O(n) walk + survivor compaction over the whole
deletion queue every frame. frameCounter is monotonic, so retireAfter is
non-decreasing down the queue and the entries ready to reclaim are always
a contiguous prefix. Switch deletionQueue from std::vector to std::deque
and pop the ready prefix off the front, stopping at the first entry still
in flight — O(ready) instead of O(queue).
Resolves#116
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
