v0.2.1

Fixed

• Require an explicit key for every aliveForever spec, including root
  bindings as well as ViewModel-to-ViewModel dependencies. Invalid
  configurations now throw ViewModelError before the builder runs, while the
  Store enforces the same rule for internal factories.

Tests

• Add root, nested, computed-key, and Store-boundary validation coverage while
  retaining single-fork, sequential unit-test execution.