Build failures with Bazel 9 (9.0.0rc2)

[sin-ack]

I tried to run bazel-diff by including it as a module in our repo (we're currently evaluating Bazel 9 to shake out any incompatibilities). I've run into the following issues when doing bazel run @bazel-diff:

1. rules_kotlin needs to be upgraded to a version that includes this commit (at least 2.1.6), since it includes rules_java which is no longer autoloaded.
2. Depending on the protos in bazel_tools in @@bazel_diff+//cli:cli-lib no longer works because bazel_tools no longer includes grpc-java as a module, which the protos need. Upstream won't fix it: depending on @bazel_tools//src/main/protobuf:deps_java_proto fails in nightly 9.0.0-pre.20250714.1 bazelbuild/bazel#26579 (comment) and wants others to vendor the protos now.

[matthewjh]

cc @tinder-maxwellelliott

[bamcmanus]

I've also encountered this issue that is giving me pause in adoption of this module.

[tinder-maxwellelliott]

Sorry everyone, was out for a bit on some paternity leave, looking at this today

[tinder-maxwellelliott]

Added tests here so we have safety going foward #300