feat: run VRF DKG during EdDSA safe MPC root creation

[danielpeng1]

Run the MPS VRF DKG inside existing EdDSA MPCv2 keygen rounds when creating a safe MPC root, and store both shares in the encrypted key material.

• Gate the VRF path on safeId so ordinary EdDSA MPCv2 wallet creation is unchanged
• Ride VRF messages as opaque blobs on MPCv2-R1/R2 (no new round values)
• Decode BitGo VRF blobs with codecs and keep only that party’s p2p openings
• Wrap signing + VRF shares in the CBOR envelope used for encryptedPrv / reducedEncryptedPrv
• Write user, backup, and BitGo keys through the existing keychain helpers so safeId lands on all three

Tests

• Envelope encode/decode for full and reduced shares
• Ordinary createParticipantKeychain still encrypts bare base64 and does not set safeId
• Safe user path encrypts the envelope and tags the keychain with safeId
• BitGo path tags safeId and does not encrypt
• VRF blob round-trip keeps only the recipient’s p2p messages
• Malformed VRF blobs are rejected

Ticket: WCN-2584

[linear-code]

WCN-2584

[github-actions]

⚠️ Unit tests are failing on Node 26.x (Current release line, non-blocking). This is not an LTS version yet, so it does not block merge, but it signals an incompatibility to fix before Node 26.x becomes LTS.

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