Create eventcore-examples crate (ADR-032)

[jwilger]

Summary

Create eventcore-examples crate per ADR-032 to house integration tests and demo applications.

Context

ADR-032 (Integration Test Crate for End-to-End Testing) establishes that:

• Integration tests should live in a dedicated crate that can depend on all other crates
• This avoids circular dependencies between eventcore and eventcore-testing
• The crate also serves as home for demo applications (Add demo application using EventCore with PostgreSQL #260)

Requirements

1. Create eventcore-examples/ crate at workspace root
2. Add to workspace in root Cargo.toml
3. Dependencies: eventcore, eventcore-memory, eventcore-testing, eventcore-types
4. Structure:
   • src/lib.rs - shared test domain types
   • tests/ - integration tests
   • examples/ - demo applications

Parent Issue

Sub-issue of #272

Related

• Add demo application using EventCore with PostgreSQL #260 - Demo applications will live here
• Implement EventCollector projector in eventcore-testing (ADR-031) #278 - EventCollector needed for test assertions