swiftpm/alignment/android are null in the JSON for a plugin whose
checks couldn't run (SPEC §3.1.2-3: "never omitted" but null on
failure) — parsed here as an all-null sentinel rather than a missing
key, since errors (checked first by every grading function) is
always non-empty whenever they're null.
Which pub.dev search(es) surfaced this plugin (SPEC §3.1.1), e.g.
["no-swiftpm", "top-downloads"]. Empty for snapshots taken before
this field existed.