Taproot feature support

[Battambang]

Note

Medium Risk
Expands supported address/derivation types and changes account discovery/creation validation and index resolution, which could affect account derivation and discovery results across networks despite strong test coverage.

Overview
Adds Taproot (P2TR) support to the snap’s keyring by allowing createAccount to accept/derive p2tr from BIP-86 derivation paths, validating addressType/path consistency, and auto-incrementing indices per (entropySource, network, addressType).

discoverAccounts now probes both P2WPKH and P2TR for each scope and still returns only accounts with transaction history. Extensive integration/unit test updates cover P2TR account creation, UTXO ops, PSBT fill/sign/broadcast, fee computation, transfers, and message signing; test utilities/constants were expanded (shared TEMPLATE_PSBT, P2TR test vectors, getNewAddress helper).

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[mikesposito]

Nice work on this! The implementation itself looks good, but I added some suggestions to improve readability, and avoid some type casts

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.