Bug: New MDX files added by promptless to bazel-docs repo get wiped by pull-from-bazel-upstream workflow

The example in #119 shows that the workflow ran and deleted the changes made by promptless. Here is the offending commit: https://github.com/bazel-contrib/bazel-docs/pull/119/commits/131d4853febe5b9c559a52481644888857940b84.

The solution here is to have promptless create PRs against https://github.com/bazelbuild/bazel

Start with the pull-from-bazel-upstream workflow and inspect the offending commit from PR #119 to understand how new MDX files are deleted. Trace how promptless changes are submitted, then verify that its documentation changes create PRs against bazelbuild/bazel rather than bazel-contrib/bazel-docs.

Written by the indexing model from the issue text.