refactor(keyring-sdk)!: remove envelope from the migration framework

[ccharly]

Remove the use of the envelope for the migration's states. This allows more flexibility for systems/data that already uses a version field with a flat shape, making it more natural too.

---

Note

High Risk
Breaking API and on-disk/vault serialization shape for any consumer of createMigrations; integrators must migrate deserialize/serialize and stored state from envelope to flat form.

Overview
Breaking change: The keyring migration framework no longer wraps state in { version, data }. Serialized state is flat—version sits next to keyring fields—and apply() returns { version, state, migrated } instead of putting payload on data.

Migration steps still receive and return inner data without version; the framework strips version before running steps and sets state.version to the chain version after (overriding any version a step returns). isVersionedState now means any plain object with an integer version, not an envelope with required data.

State must be a plain JSON object (JsonObject): unversioned null or arrays throw, and default step validation uses JsonObjectStruct rather than generic JSON. Typed chains and tests were updated for the new shapes.

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[ccharly]

@metamaskbot publish-preview

[github-actions]

Preview builds have been published. See these instructions (from the core monorepo) for more information about preview builds.

Expand for full list of packages and versions.

{
  "@metamask-previews/account-api": "2.0.0-00307a3",
  "@metamask-previews/hw-wallet-sdk": "1.0.0-00307a3",
  "@metamask-previews/keyring-api": "24.1.0-00307a3",
  "@metamask-previews/eth-hd-keyring": "15.0.0-00307a3",
  "@metamask-previews/eth-ledger-bridge-keyring": "13.0.2-00307a3",
  "@metamask-previews/eth-money-keyring": "4.0.0-00307a3",
  "@metamask-previews/eth-qr-keyring": "3.0.0-00307a3",
  "@metamask-previews/eth-simple-keyring": "13.0.0-00307a3",
  "@metamask-previews/eth-trezor-keyring": "11.0.0-00307a3",
  "@metamask-previews/keyring-internal-api": "12.1.0-00307a3",
  "@metamask-previews/keyring-internal-snap-client": "11.1.0-00307a3",
  "@metamask-previews/keyring-sdk": "3.1.0-00307a3",
  "@metamask-previews/eth-snap-keyring": "24.1.0-00307a3",
  "@metamask-previews/keyring-snap-client": "10.0.0-00307a3",
  "@metamask-previews/keyring-snap-sdk": "10.0.0-00307a3",
  "@metamask-previews/keyring-utils": "5.0.0-00307a3"
}