v3.3.0 stellar-rpc v27.1 support

Summary

This release adds support for the stellar-rpc v27.1 API: the useUpgradedAuth
simulateTransaction flag and the new getHealth ledger close-time fields. It also
fixes automatic state restore, Soroban fee-bump fee math, SEP-10 challenge
validation, and XDR uint32 decoding, adds SorobanServer injection to the
contract-client entry points, updates the contract-binding test fixtures for the
next release of the community bindings generator
(stellar-contract-bindings),
and refreshes CI dependencies.

simulateTransaction useUpgradedAuth flag (#159)

New optional useUpgradedAuth flag on SimulateTransactionRequest and, for the
contract-client path, on MethodOptions. When set, recording-mode simulation on a
supporting RPC (stellar-rpc v27.1.0+) returns ADDRESS_V2 credential entries
(Protocol 27, CAP-71) instead of legacy ADDRESS entries. The key is omitted from
the JSON-RPC params when false (the default); servers without support silently
ignore it and return legacy entries — detect support by inspecting the credential
arm of the returned entries. Additive and opt-in; existing call sites are
unaffected.

getHealth ledger close times (aea7b1d)

GetHealthResponse gains latestLedgerCloseTime and oldestLedgerCloseTime, the
unix timestamps (seconds) at which the latest and oldest ledgers closed, returned
by stellar-rpc v27.1.0+. The values are exposed as strings, consistent with the
close-time field on SendTransactionResponse. On older servers the fields are
absent from the response and parse as null.

Bug fixes (#158, 1b37927)

• Automatic state restore (AssembledTransaction.simulate with restore: true):
  a successful restore no longer throws "Automatic restore failed"; the
  transaction is rebuilt with the bumped sequence number and re-simulated,
  keeping its original operation and configured fee, and the restore
  transaction's own simulation is awaited before signing.
• FeeBumpTransactionBuilder.setBaseFee for Soroban transactions: the inner
  transaction's resource fee is excluded from the per-operation rate check and
  added once to the total (baseFee * (operations + 1) + resourceFee); the
  minimum rate for inner fees not divisible by the operation count is rounded up.
• SEP-10 validateChallenge: the first operation's data value is validated as
  required by the spec (present, 64 bytes, base64-decoding to a 48-byte nonce);
  non-compliant challenges now fail with a challenge validation error instead of
  an unhandled TypeError.
• XDR decoding of unsigned int (uint32) values: values of 2^31 or greater no
  longer decode as negative numbers, correct across native and web (dart2js)
  platforms.

API additions (#158)

ClientOptions, InstallRequest and DeployRequest accept an optional server
parameter with a preconfigured SorobanServer, used for all RPC calls instead of
constructing one from rpcUrl. This allows reusing a single RPC connection
across operations and injecting custom HTTP client configurations.

Contract-binding fixtures and tests (#157)

The checked-in fixtures for the community bindings generator are regenerated for
the generator's next release, and two new fixtures with testnet integration tests
verify that the generated Dart code runs correctly:

• BindingsSpecTestContract, generated from the generator repository's
  reference contract, covers the entire contract-spec type surface.
• OptionShapesContract covers option values in nested positions and the
  Dart-keyword-escaped default method.

Other

• Compatibility matrices: refresh the Soroban RPC baseline to v27.1.1
• Bump pinned GitHub Actions (checkout v7.0.0, cache v6.1.0, codecov-action
  v7.0.0, claude-code-action v1.0.171) via Dependabot
  (#154,
  #155,
  #156) and a
  release-commit pin refresh