Resolve "Claude 4.0 Sonnet Code Review Summary Rollout Plan"

What does this MR do and why?

reference !183213 (merged) and gitlab-org/modelops/applied-ml/code-suggestions/ai-assist!2066 (diffs)

issue https://gitlab.com/gitlab-org/gitlab/-/issues/545693

this MR should be reviewed together with gitlab-org/modelops/applied-ml/code-suggestions/ai-assist!2695 (merged)

References

Screenshots or screen recordings

Before	After

1.enable the ff:

[6] pry(main)> Feature.enabled?(:summarize_code_review_claude_4_0_sonnet)
=> true

1. add a couple of code reviews

2. click on finish review

3. click on add summary

4. check AIGW log and find: Claude 4.0 Summarize Review

2025-06-06 10:18:29 [info     ] Returning prompt from the registry correlation_id=01JX2SQ0RMJFEESD0QT3HBFN1R prompt_id=summarize_review/base prompt_name='Claude 4.0 Summarize Review' prompt_version=2.1.0

How to set up and validate locally

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.

Related to #545693