Locates a usable go binary for runtime IPC helpers. Resolution order:
options(mangoro.go_path)Sys.getenv("MANGORO_GO")PATHentries and platform defaults viago_binary_candidates()
Candidates are validated by running go version and checking the minimum
required Go version from the vendored go.mod. Errors reference the
detected OS/arch using user-friendly labels (e.g., macOS arm64).