Calling get_github_token() without arguments always invoked LangGraph get_config internally,
which broke tests that only patch agent.middleware.open_pr.get_config and failed outside
runnable context.
Extend get_github_token with an optional runnable config mapping; the middleware passes
the config dict already resolved from get_config(). Request GitHub App installation tokens
only after detecting sandbox/repo changes worth publishing.
Fixes failing Agent unit tests in tests/test_open_pr_middleware.py.
6ef70823be