Stellar Soroban error decoder library

[truthixify]

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

Context

When a Soroban contract reverts, the raw error code is uninformative. Today consumers either ignore it or write per-contract decoders. Centralize this as a registry-based decoder shipped with the SDK.

Scope

• decodeSorobanError(error, contractId?) returns { code, name, description, suggestedFix }
• Built-in registries for the four Wraith Stellar contracts (announcer, registry, sender, names, splitter)
• Pluggable: consumers can register custom contract error registries
• Falls back to raw code if unknown
• Tests against fixture error responses

Acceptance criteria

• Decoder + registries for Wraith contracts
• Plugin API
• Documentation
• Demo follow-up to use in error toasts

Files to start with

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