v0.6.0

Forecasts in the browser, regressors forecast by their own models, and mean absolute scaled
error. Existing code works as before; only a damaged calendar file reports a different error
reason.

Added

• Browser and bundler support. The same package and import now work in browsers. Vite (build
  and dev server), webpack and Rspack need no configuration; esbuild needs the engine binary
  copied next to the bundle. Browsers download the WebAssembly engine once per page, and each
  country holiday calendar is its own chunk, loaded the first time it's used. Tested in Chromium,
  Firefox and WebKit, which give exactly the same forecasts as Node.js. Node.js still loads the
  engine synchronously, so Effect.runSync keeps working there. See
  Browsers and bundlers.
• Regressors forecast by their own models. Set predictor: true, or options, on a regressor,
  like Python's regressor_predictor, and fit fits a model to that regressor's history.
  predict uses its forecast in every row after the history, so future rows need no value for
  it. Intervals include each regressor model's own uncertainty, as in Python, and saved models
  keep these models. When one of them fails, FittingError and PredictionError name it in a
  new optional regressor field. See
  Forecasting a regressor.
• Mean absolute scaled error (MASE). scaledErrorMetric divides each forecast's error by a
  naive rule's average error on the rows its round trained on, repeating either the previous row
  or the value a set time earlier. It's a metric definition, so performanceMetrics,
  comparePerformance and searchModels accept it. Rounds it can't scale fail with the new
  MetricScaleError. Python Prophet has no scaled metrics. See
  Scaled errors.
• New spans for regressor models and scaledErrorMetric. See the
  tracing guide.

Changed

• Country holiday calendars are loaded as JSON modules, once per process, instead of being read
  from disk on every fit. Each use still checks the file's format version and contents. The
  byte-count and SHA-256 checks against the bundled catalog are gone, and a calendar file that
  isn't valid JSON now fails with snapshot-unavailable instead of corrupt-snapshot.

Verification against Python Prophet

• New fixtures check regressor models' forecasts against regressor_predictor, and that
  their draws widen future intervals as much as Python's do.
• New benchmarks for regressors forecast by their own models, on flat and linear growth,
  checked against Python Prophet for forecasts, uncertainty ranges and cross-validation.
• Twelve-fold cross-validation and model search benchmarks, one for each growth. Python
  Prophet is timed sequentially and with cross_validation's parallel="threads" and
  parallel="processes", which must give the same forecasts and scores as running sequentially.
  Effect Prophet still runs folds one at a time, and is faster than either parallel mode.
• MASE benchmarks on flat and logistic growth. Python Prophet has no MASE, so the Python side
  registers it with register_performance_metric. Each fold's scale must match, and overall
  scores may differ only as much as the two libraries' forecasts do.

Full Changelog: v0.5.1...v0.6.0