2.3.0

Sync upstream alien-signals^v3.2.1

New Features

• effect() can return a cleanup callback; effectScope nesting and
  propagation are improved.

Bug Fixes

• Corrected disposal and cleanup ordering for effects and computeds.
• Preserved subscriptions across re-runs; fixed propagation for writes inside
  effects.
• Made updates resilient to dependency-graph mutations; tightened cleanup
  timing.

Documentation

• API and guide updated to document generic effect callbacks and cleanup
  behavior.

Tests

• Added comprehensive tests covering cleanup, teardown, scopes, and mutation
  cases.