acquire

Acquire a ref-counted projection.

If no entry exists for spec.key, one is created (allocating a StreamStore seeded with spec.initial) and — when a thread is currently bound — its runtime is opened immediately. If an entry already exists, its ref count is incremented and the existing store is returned.

The returned release() is idempotent: calling it more than once is a no-op. When the ref count drops to zero, the entry is removed and its runtime disposed (best-effort, never throws into callers).

Safe to call from any framework lifecycle hook. Subsequent calls for the same spec.key always return the same store reference for the lifetime of the controller, so consumers can rely on store identity.