feat(sim): Emit exact diagnostic_events matching Soroban CLI - Issue #341

[unixfundz]

Overview

Fixes erst-sim diagnostic event emission to achieve 1:1 parity with
identical rust-soroban-env execution outputs.

Changes

Core Implementation

• in_successful_contract_call fix: Corrected inverted logic — was
  set to event.failed_call instead of !event.failed_call in both the
  main event emission path and categorize_events
• contract_id serialization: Replaced Rust Debug format ({:?})
  with lowercase hex encoding, matching Soroban CLI output
• topics and data serialization: Replaced Rust Debug format with
  base64-encoded XDR via WriteXdr, matching Soroban CLI output exactly
• runner.rs cleanup: Removed broken CostModel/set_model calls
  unavailable in soroban-env-host v25 public API
• Dead test removed: Deleted test_decode_vm_traps referencing
  non-existent decode_error function

Testing

• Added simulator/tests/diagnostic_events.rs with 6 tests:
  • in_successful_contract_call_is_inverse_of_failed_call
  • topics_serialize_to_valid_xdr_base64
  • data_serializes_to_valid_xdr_base64
  • contract_id_encodes_as_hex_without_debug_formatting
  • event_type_field_matches_allowed_values
  • event_body_is_v0

Verification

• All 12 tests pass (cargo test)
• cargo clippy -- -D warnings passes with zero warnings
• No lint suppressions added
• Backward compatible with existing simulation API

Related Issues

Closes #341

Type of Change

• Bug fix
• New feature (tests)
• Breaking change
• Documentation update

Checklist

• Code follows project style guidelines
• Self-review completed
• Tests added/updated
• No new linting issues
• Changes verified locally

[dotandev]

fix conflicts