[Experiment] Duo Code Review
## Context
See https://gitlab.com/groups/gitlab-org/-/epics/13008+.
## Goal
Release a first iteration of Duo Code Review internally to GitLab team members as an Experiment. This will provide initial real-world feedback and guide future iterations in https://gitlab.com/groups/gitlab-org/-/epics/13476.
For simplicity, Duo Code Review will be triggered by a quick action named `/duo_code_review`.
## Timeline (internal release)
We shipped this Experiment internally in %17.5 (on 2024-09-30).
<details><summary>Project plan (archived)</summary>
- Week of Sept 16th:
- :white_check_mark: Deploy latest prompt version - https://gitlab.com/gitlab-org/gitlab/-/merge_requests/166111
- Week of Sept 23rd:
- :white_check_mark: Refine success criteria by building MR testing data set - https://gitlab.com/gitlab-org/gitlab/-/issues/490991
- :white_check_mark: Iterate on prompt using Langsmith only, quick feedback cycles
- Week of Sept 30th:
- :white_check_mark: Pick most promising prompt, build it into the monolith - https://gitlab.com/gitlab-org/gitlab/-/merge_requests/167156
- :white_check_mark: Release Experiment internally
- :hourglass_flowing_sand: Internal testing on gitlab.com
- Week of Oct 7th:
- :hourglass_flowing_sand: Internal testing on gitlab.com
- Final touches/fixes
- :x: Release Experiment externally (postponed due to scope increase)
</details>
## Timeline (external release)
We shipped this experiment externally in %"17.9" (on 2025-02-13).
For detailed project updates, see https://gitlab.com/gitlab-org/ai-powered/daily-updates/-/issues/7 (internal).
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