Serve archived job logs from the job trace API through Workhorse

What does this MR do and why?

This MR default-enables the ci_job_trace_api_archived_log_via_workhorse feature flag, so self-managed and Dedicated instances get it as well as GitLab.com. The flag has been at 100% on GitLab.com since 2026-09-22, with latency neutral to better and a large drop in external range requests to object storage. The one issue found during rollout, truncated log bodies for Duo Workflow HTTP actions, is fixed by !258036 (merged), which ships in the same milestone.

References

• Rollout issue: https://gitlab.com/gitlab-org/gitlab/-/work_items/629437
• Feature issue: https://gitlab.com/gitlab-org/gitlab/-/work_items/629424
• Introducing merge request: !255994 (merged)
• Workhorse fix merge request: !258036 (merged)

Screenshots or screen recordings

Not applicable, no UI change.

How to set up and validate locally

1. In the rails console, run Feature.enabled?(:ci_job_trace_api_archived_log_via_workhorse) and confirm it returns true without enabling the flag.
2. Fetch the trace of an archived job through the API and confirm the response is served by Workhorse, for example by sending a Range: bytes=0-99 header and confirming the response comes back as 206.

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.