Update the ATVM git guide so push examples do not hardcode origin/main.
Prefer the operator-specified remote and branch when provided, and otherwise draft a generic SSH-prefixed git push command or use the remote/branch already established in context.
Prefer failing and terminal host results when merging supplemental
subrun artifacts so a later partial artifact cannot overwrite a more
authoritative outcome.
Also point ATVM agent guidance at the ATVM-specific git guide and add
that guide to document draft-only commit handling and the default SSH
command pattern.
