Second of three stacked PRs (base: [1/3] connect + auth). Wires the
statement-execution + result-read path:

- SeaSessionBackend.executeStatement: real implementation — runs SQL via the
  napi Connection and returns a SeaOperationBackend (replaces [1/3]'s stub).
- SeaOperationBackend: fetch pipeline (napi Statement.fetchNextBatch →
  SeaResultsProvider → ArrowResultConverter → ResultSlicer) plus operation
  cancel/close/finished via the SeaOperationLifecycle helpers.
- SeaResultsProvider / SeaArrowIpc / SeaArrowIpcDurationFix: Arrow IPC decode
  for inline + CloudFetch result batches (the duration-fix pre-processor
  rewrites Arrow Duration → Int64 so apache-arrow@13 can read it).
- ArrowResultConverter: constructor now takes the neutral { schema? } shape so
  both the Thrift and SEA backends construct it without an adapter.
- flatbuffers pinned to 23.5.26 to match apache-arrow@13's nested copy.

Tests: executeStatement + openSession forwarding, M0 datatype round-trip
through the shared converter (primitives + ARRAY/MAP/STRUCT), multi-batch
streaming, and the neutral-metadata converter contract. Full INTERVAL-type
value parity + exhaustive operation-lifecycle coverage land in [3/3].

Co-authored-by: Isaac
Signed-off-by: Madhavendra Rathore <madhavendra.rathore@databricks.com>