📦 Add Bazel extension to expose transitive dependencies via setup.bzl

We should provide a Bazel extension (setup.bzl) in this module to simplify integration for downstream consumers and follow best practices for reusable Bazel modules.

🎯 Motivation

Currently, downstream projects that use score_docs_as_code and its macros must also manually declare:

bazel_dep(name = "score_python_basics")

in their MODULE.bazel, even though it’s only used indirectly by macros from this module.

This violates the principle of encapsulated, reusable modules and puts an unnecessary burden on consumers.

✅ Goals

• Provide a setup.bzl file with a public function (e.g. setup_dependencies(ctx)) that:
  • Uses ctx.use_repo() to expose transitive repos like score_python_basics
  • Optionally sets up further repo-level initialization (e.g. venv, toolchains)
• Document this extension usage in the module README
• Adapt examples and tests to use this new aproach

📐 Proposed Structure

setup/setup.bzl

def setup_dependencies(ctx):
    ctx.use_repo(dependency = "score_python_basics", repo_name = "score_python_basics")

Usage in downstream MODULE.bazel

bazel_dep(name = "score_docs_as_code", version = "...")

use_extension("@score_docs_as_code//setup:setup.bzl", "setup")
setup.setup_dependencies()

📝 Additional Ideas

• Consider converting frequently-used macros (e.g. define_docs_env) into actual extensions using tag_class and module_extension.
• Possibly wrap setup of the Python venv and Sphinx-Needs dependencies into a more declarative Bazel extension API in the future.