v0.6.0

Added

• Optional FetchedAsset.open() CSV reading through usdata[pandas], including
  ERDDAP units metadata, string identifiers/codes, explicit dtype/date/column/row
  options, and a fetch-to-analysis example. Opening leaves raw bytes and provenance intact.

Changed

• Test core-only and pandas installations in CI and installed-wheel checks.
• Check versioned source-only documentation notices during validation so release
  PRs cannot carry known stale availability wording.
• Focus v0.6 on optional CSV readers and practical usage; NASA, model output,
  climate grids, and remote caching remain follow-up work.