[drah9991]

Summary

This PR implements a uniform event-versioning policy across all Soroban contract events. It migrates the TypeScript client away from fragile positional decoding toward strict, name-based schema validation, ensuring that reordered or malformed payloads are explicitly rejected rather than silently misparsed.

Related Issue(s)

Closes #496

Type of Change

• Feature
• Fix
• Refactor
• Documentation
• Chore

Description

1. Smart Contract (Rust)

• Added schema_version: u32 to all previously unversioned events (e.g., AssetAllowlisted, ContractPaused, AdminTransferProposed, etc.).
• Injected the global EVENT_SCHEMA_VERSION constant into every emit_* function.
• Updated all Rust assertions in test.rs to account for the new payload shape.
• Documented the event-versioning policy in events.rs alongside the ABI stability notes.

2. TypeScript Client & Decoder

• Removed Positional Decoding: Completely stripped index-based parsing (payload[0]). The client now requires named ScMap payloads resolved by Soroban symbols.
• Centralized Validation: decodeSorobanEvent and the codec now enforce schemaVersion against the expected constant. Unsupported versions or missing fields trigger a structured rejection ({ type: 'unknown', name: '...' }).

3. CI & Tooling

• Updated schema.json and tightened the generator template to make schema_version mandatory.
• Extended the ABI drift script (check-client-drift.mjs) to strictly compare ordered Rust fields, schema properties, and client declarations.

Testing Evidence

• Rust Smart Contract: Executed cargo test. All 202 tests passed successfully.
• TypeScript Client: Wrote a table-driven test suite in events.test.ts covering 3 scenarios (success, unsupported version, and malformed/reordered payload) for all 14 contract events. Executed npm test locally, with all 105 tests passing.
• CI Drift: Executed node soroban/scripts/check-client-drift.mjs without errors, ensuring ABI schema matches the Rust source and TS client definitions.

Screenshots

Not applicable (Smart contract, client library, and CI tooling changes only).

Checklist

• Code builds successfully
• Tests added/updated where applicable
• Documentation updated if needed
• Linked issue referenced
• Ready for review