Add the Enterprise Integration Patterns Message Store pattern as a production-ready PatternKit slice.
Scope:
- Runtime fluent API for durable message persistence, lookup, replay metadata, and retention-safe querying.
- Source generated path for strongly typed message store modules.
- TinyBDD coverage for runtime, source generators, attributes, examples, and production-readiness catalog entries.
- Real-world IServiceCollection / Generic Host example showing an importable message audit/replay store.
- Documentation: pattern guide, generator guide, example guide, ToC/catalog updates.
Acceptance:
- No manual assertions in new tests; use TinyBDD scenarios/assertion trees.
- PR lands green on main.
Add the Enterprise Integration Patterns Message Store pattern as a production-ready PatternKit slice.
Scope:
Acceptance: