v10.0.0

Reconciles upstream OpenAPI 3.27.0 content drift plus AsyncAPI / perps
OpenAPI changes (Closes #496, #497). Breaking for callers of multivariate
lookup (REST + WS).

Removed (breaking)

• multivariate_collections.lookup_tickers() (sync + async) and models
  LookupTickersForMarketInMultivariateEventCollectionRequest /
  LookupTickersResponse. Upstream deleted
  PUT /multivariate_event_collections/{collection_ticker}/lookup and the
  matching schemas. create_market() remains (still deprecated).
• WS subscribe_multivariate() plus MultivariateMessage /
  MultivariatePayload / SelectedMarket. AsyncAPI removed the
  multivariate channel and multivariateLookupPayload schema.
  subscribe_multivariate_lifecycle() is unchanged.

Added

• portfolio.intra_exchange_transfers() /
  intra_exchange_transfers_all() /
  get_intra_exchange_transfer(transfer_id) (sync + async) —
  GET /portfolio/intra_exchange_instance_transfers and
  GET /portfolio/intra_exchange_instance_transfers/{transfer_id}.
  Model: IntraExchangeInstanceTransfer (amount is fixed-point dollars).
  Complements PerpsClient.transfers.transfer_instance() (POST create).
• MultivariateEventCollection.exchange_index (int | None) — optional
  exchange shard inherited from the collection's series.
• Perps MarginMarket.long_leverage_estimates /
  short_leverage_estimates (dict[str, MultiplierDecimal] | None).

Spec notes

• Core OpenAPI info.version still 3.27.0 (paths 92→92; 103→104 operations;
  103 mapped). Still unimplemented on the core client:
  POST /portfolio/intra_exchange_instance_transfer (use
  PerpsClient.transfers.transfer_instance()).
• AsyncAPI: channels 15→14 (multivariate removed).
• Perps OpenAPI: additive optional leverage side maps on MarginMarket.