v0.3.1 - EEGDash live-API fixes + real example

Patch release: validate the EEGDash backend against the live API and add a real example.

Fixed

• Map EEGDash dataset metadata to the real API field names: read the DOI from
  dataset_doi (stripping the doi: prefix) and the citation from author_year.
• Read BIDS entities (subject/session/task/run) whether nested under entities or
  flattened at the top level (the live find() records use the flat form).

Added

• A real example from a live scan of ds002718 (Wakeman face-processing, 18 subjects):
  examples/ds002718.md and examples/ds002718.provenance.json.

Verified

• 26 tests; ruff lint + format; CI green on Windows/Linux x Python 3.11/3.12.