Entitas v1.5.1

Fixes reactive batch ownership and exception cleanup, preserves nested group notifications, and reduces temporary allocations. Standard matchers now share groups by structural criteria while custom matcher subclasses retain their predicates and identity.

Compatibility: standard matcher criteria are snapshotted at registration. Custom matcher criteria must remain fixed after registration. Contexts, groups, and collectors still require a single owner. See CHANGELOG.md for details.

Validation: 368 passing specs on Crystal 1.14.0 and 1.22.0; all 12 PR checks passed. Requires Crystal >= 1.14.0, < 2.0.0.

Changes: #6
Full changelog: v1.5.0...v1.5.1