Add Aegis event compatibility tests

[Johnpii1]

Description

This PR adds a comprehensive integration test suite to verify contract event compatibility and prevent regressions that could break SDKs, dashboards, and indexers when event topics or payload structures change. It also updates the event documentation to reflect the verified event schema and improve guidance for downstream consumers.

Related Issues

Closes #166

Completion Table

Acceptance Criterion	Status	Implementation Evidence	Test Evidence	Documentation Impact
AC 1: Add integration tests covering contract event compatibility across supported event types.	Complete	Added tests/event_compatibility.rs with compatibility assertions for compliance, minting/transfers, roles, governance, asset lifecycle, metadata, and issuer separation events.	cargo test --test event_compatibility (5/5 tests passed).	N/A
AC 2: Reuse the existing test harness for deterministic event validation.	Complete	Reused tests/support/mod.rs to provide deterministic addresses and typed event assertions.	Verified by the integration compatibility test suite.	N/A
AC 3: Update documentation to reflect the compatibility tests and event payload expectations.	Complete	Updated docs/events.md with compatibility test references, SDK fixture guidance, corrected lifecycle attribution, and payload documentation.	Documentation reviewed alongside passing tests.	Updated docs/events.md.

Detailed Traceability Mapping

Acceptance Criteria	Implementation	Storage & State Changes	Events Emitted	Test Coverage	Security/Safety Controls
AC 1: Event compatibility coverage	Added tests/event_compatibility.rs with integration-level compatibility assertions.	None	Existing contract events verified only (no changes).	Integration tests validate topics and payload shapes across supported event categories.	Ensures downstream integrations remain compatible with emitted event schemas.
AC 2: Documentation alignment	Updated docs/events.md with compatibility testing guidance and corrected payload documentation.	None	None	Verified alongside integration test execution.	Reduces documentation drift between implementation and SDK consumers.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Chore (refactoring, build tools, etc.)

Additional Context

Testing

• ✅ Ran cargo test --test event_compatibility — all 5 compatibility tests passed.
• ✅ Ran cargo test — full test suite passed, including existing unit tests, SDK fixture tests, and the new compatibility tests.