README documents supported key patterns, unique/sparse/multikey behavior,
planner rules (multikey two-bound range fallback, sparse/null bail, the
_id fast-path guards), and v1 limits plus the two pre-existing issues the
work surfaces (drop-collection resurrection, compact log_bytes).
e2e3.js exercises createIndex/getIndexes/dropIndex/dropIndexes, the
unique-constraint 11000 path, compound, sparse, and descending indexes
through the official Node driver.
