annotate - buildkite-agent: Argument list too long

Error happens when sending a long list (like 240 lines) of warnings to annotate
via
`buildkite-agent annotate "${ANNOTATION}" --context "${CONTEXT}" --style $STYLE --append`

Start at the buildkite-agent annotate entry point and reproduce the failure with a warning list of roughly 240 lines using the command shown. Trace how the annotation is sent and verify that long warning lists no longer fail with an argument-list-too-long error.

Written by the indexing model from the issue text.