feat(sdk-core): add PolyxSwitchValidatorOptions for multi-nomination

[joshisakshi]

TICKET: SI-842

Summary

• Add PolyxSwitchValidatorOptions to @bitgo/sdk-core for POLYX multi-validator nomination switch requests
• Widen IStakingWallet.switchValidator() and StakingWallet.switchValidator() to accept the new options type
• Include PolyxSwitchValidatorOptions in the internal createStakingRequest() options union

POLYX switch-validator replaces the full nomination set and does not use validator or amount. The staking-service already accepts { delegationId, validators }; this change aligns the SDK types with that contract so UI callers no longer need as SwitchValidatorOptions.

Motivation

bitgo-ui / bitgo-retail currently type-assert the switch-validator payload when submitting POLYX multi-nomination requests, because SwitchValidatorOptions requires validator and amount. This follows the same approach as TaoSwitchValidatorOptions for coin-specific switch payloads.

Changes

File	Change
modules/sdk-core/src/bitgo/staking/iStakingWallet.ts	Add PolyxSwitchValidatorOptions; update switchValidator signature
modules/sdk-core/src/bitgo/staking/stakingWallet.ts	Import new type; update switchValidator + createStakingRequest union

No runtime behavior change — createStakingRequest already forwards options as-is to staking-service.

Follow-up (separate PRs)

After this SDK version is published and bumped:

1. bitgo-ui — remove payload as SwitchValidatorOptions in useCreateSwitchValidatorRequestMutation.ts; use PolyxSwitchValidatorOptions in the payload union
2. bitgo-retail — same cleanup if applicable
3. bitgo-microservices — no WP/SDK route changes expected; staking-service already supports the payload

Test plan

• yarn compile in modules/sdk-core
• Existing stakingWalletCommon switch-validator test still passes (no new test added — consistent with no dedicated test for TaoSwitchValidatorOptions)
• After SDK bump in UI: POLYX multi-nomination switch validator submits without type assertion

[linear-code]

SI-842

[Doddanna17]

commented

[Doddanna17]

lgtm