Geo Phase 2: 2dsphere + 2d index acceleration
v0.3.0a26 adds index acceleration for everything Phase 1 shipped. 2dsphere indexes use S2 cell coverings (via s2sphere): each indexed geometry writes its covering cells plus every ancestor back to level 0, mirroring real mongod's S2 scheme; queries compute their own covering+ancestors and do exact point-lookups against the entries table, with a Shapely / haversine verifier filtering false positives. 2d indexes use bit-interleaved geohash buckets at the user's bits precision (default 26), with a single (lo, hi) bbox range scan per query.
CI got faster too: ccache is now cached across cibuildwheel runs, halving the publish-workflow time.