test(distributed): scan staging overrides package-wide

Discover direct FileStagingClient backend overrides from every non-test source file in the nodes package, and locate that package without relying on runtime source paths so coverage inventory checks survive trimpath builds.

Assisted-by: Codex:GPT-5 [apply_patch] [exec_command]
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f