Feat(paymaster): Jito bundles SponsorBundle support

[thewuhxyz]

Summary

Adds Paymaster SDK support for sponsoring Jito bundles through the new /paymaster/sponsor/bundle endpoint.

Changes

• Add sponsor-bundle API client/types.
• Add SDK idempotency key support for submit operations.
• Add Jito bundle helpers for:
  • creating paymaster-funded tip instructions
  • detecting existing Jito tips
  • validating minimum tip amounts
• Add signAndSendBundle APIs for classic and kit clients.
• Add serialized bundle submit helpers.
• Add a jito-classic paymaster example.
• Add .env.example for the Jito bundle example.
• Improve API error handling for gRPC-transcoded responses.

Test Notes

• bun --filter '@swig-wallet/paymaster-core' typecheck
• bun --filter '@swig-wallet/paymaster-classic' typecheck
• bun --filter '@swig-wallet/paymaster-kit' typecheck
• bun --filter '@swig-wallet/paymaster-core' build
• bun --filter '@swig-wallet/paymaster-classic' build
• bun --filter '@swig-wallet/paymaster-kit' build

Manual E2E against local backend with Jito bundle flow completed successfully.

[edo-chan]

Requesting changes on two bundle-contract blockers:

1. packages/paymaster/kit/src/index.ts:263-289 treats an ALT-loaded paymaster-to-Jito transfer as an absent tip and appends a second static tip. The returned bundle still contains the original ALT-backed paymaster debit, which the merged backend rejects as disallowed paymaster debit. Please reject this input, or otherwise replace it safely before signing, instead of returning a bundle guaranteed to fail. Update packages/paymaster/kit/tests/jito.test.ts:37-50, which currently asserts the invalid two-instruction result.

2. packages/paymaster/core/src/client.ts:215-220 trusts the success response without validating bundle cardinality or required fields. Please require non-empty request and bundle IDs, a string signature array with exactly one signature per submitted transaction, and a decimal u64 estimated_spent_by_paymaster. Add a true two-transaction ordered success test plus malformed-cardinality coverage; the current test at packages/paymaster/core/tests/client.test.ts:19-58 proves only a one-item response.

The endpoint and field names, unchanged signed-byte submission, and mainnet, tip, and fee-payer checks otherwise align with the merged backend contract.

[edo-chan]

Approving overall. The previously noted bundle preparation and response-validation items are non-blocking follow-ups.