Crow cannot interpolate the workflow-level OS/OS_VERSION form variables inside
an environment: block (only matrix variables work there), so exporting them
broke pipeline parsing with "unable to parse variable name".
Instead, derive platform + arch inside build-all.R from the running container,
mirroring bincraft's own codename -> platform mapping and machine -> arch
detection. This keeps the already-built dedup pre-filter effective without
depending on CI-injected env vars, and degrades to a length-1 NA (querying
nothing) for an unmapped codename rather than crashing.
pat-s
bc2f6f1517