v2.0.0

Bump Directory.Build.props to 2.0.0 #major (#75)

#74's class→trait conversion of Pipe[T] was binary-incompatible
but shipped as v1.3.7 because the commit didn't carry a #major
marker for the version-bump action. Force the next release to 2.0.0
so dependabot picks it as a major bump and skips auto-merge in
consumers (per the dependabot-auto-merge.yml major-skip rule).

Same code as 1.3.7; only the version number changes.

Co-authored-by: Claude Opus 4.7 (1M context) noreply@anthropic.com