Use buildkite-agent annotate to attach Markdown-formatted status information to a build or job in the Buildkite UI, with configurable style, context, and append/update behavior.

Documented steps

1. Usage: `buildkite-agent annotate [body] [options...]`, run from within a job. Body can be a CLI argument or piped stdin, e.g. `cat annotation.md | buildkite-agent annotate --style "warning"`. Doc: https://buildkite.com/docs/agent/cli/reference/annotate
2. Bodies are written in CommonMark Markdown with GitHub Flavored Markdown extensions. Maximum size of each annotation body is 1MiB.
3. Set visual style with `--style` (env $BUILDKITE_ANNOTATION_STYLE): one of success, info, warning, or error, e.g. `buildkite-agent annotate --style "success" --context "junit"`.
4. Use `--context <value>` (env $BUILDKITE_ANNOTATION_CONTEXT, 100-character limit) to give the annotation a unique identifier; re-running annotate with the same context updates that annotation instead of creating a new one, and omitting --context targets the default context.
5. Use `--append` (env $BUILDKITE_ANNOTATION_APPEND) to append new content to an existing annotation's body (matched by context) instead of replacing it.
6. Use `--priority <1-10>` (default 3) to control display order — priority 10 shows first, priority 1 shows last — and `--scope build|job` (default "build") to control where the annotation is displayed.
7. You can update only the style of an existing annotation by omitting the body and providing a new `--style` value while reusing the same `--context`.
8. Remove an annotation with `buildkite-agent annotation remove`. Doc: https://buildkite.com/docs/agent/cli/reference/annotate