Stellar Soroban contract spec extraction helper

[truthixify]

Tier: M (2-4 days) Type: feature

Context

Tooling that wants to interact with arbitrary Wraith deployments needs to discover the contract's spec dynamically. Stellar CLI can extract spec from a deployed contract; expose this in the SDK.

Scope

• extractContractSpec(contractId, network) returns parsed spec (function signatures, types)
• Uses Soroban RPC's contract data endpoint
• Caches results per (contractId, version)
• Generates TypeScript types on demand (optional helper)

Acceptance criteria

• Helper + tests
• Integration test against deployed Wraith contracts
• Type generation helper (optional flag)
• Documentation

Files to start with

• New: sdk/src/chains/stellar/spec.ts