Stellar multisig helpers for stealth withdrawals

[truthixify]

Tier: L (1-2 weeks) Type: feature

Context

Stellar's native multisig is a powerful primitive. Users with multisig source accounts may want to withdraw stealth funds requiring multi-signature approval. Build helpers that compose this.

Scope

• buildMultisigStealthWithdraw({ stealthAddress, destination, requiredWeight, signers }) returns transaction needing N signatures
• addStealthMultisigSigner(tx, signerKey) appends signature
• isStealthMultisigReady(tx) checks if threshold met
• Validates against on-chain account config
• Documentation walks through a 3-of-5 example

Acceptance criteria

• Helpers + tests
• Integration test on futurenet with real multisig account
• Documentation
• Demo follow-up for multisig withdraw UI

Files to start with

• New: sdk/src/chains/stellar/multisig.ts