fix: handle transitive dependencies in TreeScope

[seraphr]

Summary

This PR fixes #747, where converting @aws-sdk/middleware-sdk-s3 generated Scala code that failed to compile with an inherits conflicting members error.

The root cause was that TreeScope only considered direct dependencies. In this case, methods inherited through transitive dependencies were not visible during generation, so the converter emitted members such as serializeRequest without recognizing that they should override an inherited definition.

Changes

• add a reproduction test for aws-middleware-s3
• resolve transitive Scala.js dependencies when building TreeScope

Result

With the transitive dependency graph available during generation, the converter no longer emits the conflicting member definition for S3RestXmlProtocol

Closes #747.