feat: add eddsa MPCv2 SMC utils

[kisslove-dewangan]

TICKET: WCI-242

[linear-code]

WCI-242

[Marzooqa]

Overall structure is correct — the 2-round key-gen flow (no round 3) is intentionally different from ECDSA because MPS EdDSA DKG only requires 2 BitGo rounds. uploadClientKeys is a faithful copy of the ECDSA version. Three issues below; one is a potential runtime failure on every call.

No tests added. The ECDSA MPCv2SMCUtils also has no unit tests, but this is still a gap — at minimum keyGenRound1BySender and keyGenRound2BySender should have state-assertion failure tests and a happy-path test using a stub sender.

[Marzooqa]

See inline comments.

[lokesh-bitgo]

@claude Please do a thorough review of this PR.

Focus especially on:

• any bugs or incorrect logic in the changes
• whether these changes could impact existing flows or cause regressions
• whether the implementation is aligned with the requirement/design
• whether the changes are correct and complete
• missing edge cases, validation gaps, and test coverage gaps

Please call out concrete issues clearly and separate them by severity if possible.

[lokesh-bitgo]

@claude

[kisslove-dewangan]

note: API spec breaking is intentional as I've confirmed from change owner, thread: https://bitgo.slack.com/archives/C057BHBRG4B/p1779958910469849

[lokesh-bitgo]

Overall looks good. Please add happy path test for the keyGenRound2 (enterprise) enterprise wrapper in follow up PR.

all feedback incorporated