import error from `HashTreeCollections`

This is a weird error… code I have that worked fine from 1.3.0 from importing `Collections` is now breaking: ```swift import Collections public func f(_: TreeDictionary<Int, Int>) { } ``` Fails now with an error: ```text Cannot use generic struct 'TreeDictionary' here; 'HashTreeCollections' was not imported by this file ``` Is this intentional? I am surprised that importing the "umbrella" would not include all the subpackages. Hmm… ### Information - **Package version:** 1.4.0 and 1.5.0 - **Platform version:** macOS 15.7.7 (24G720) - **Swift version:** swiftlang-6.2.4.1.4 clang-1700.6.4.2 ### Checklist - [x] If possible, I've reproduced the issue using the `main` branch of this package. - [x] I've searched for [existing GitHub issues](https://github.com/apple/swift-collections/issues).