- Add lastRecenterTimestamp to track recenter interval for TWAP
- Increase pool observation cardinality to 100 in constructor
- In _scrapePositions, use pool.observe([elapsed, 0]) to get TWAP tick
over the full interval between recenters; falls back to anchor midpoint
when elapsed==0 or pool.observe() reverts (insufficient history)
- Add test_twapReflectsAveragePriceNotJustLastSwap: verifies TWAP-based
VWAP reflects the average price across the recenter interval, not just
the last-swap anchor snapshot
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>