Add the ability to summarize a workflow flow and persist the result to a `summary` field on the workflow record. ## Problem Currently, workflows do not have a way to capture or store a human-readable summary of what the flow does. This makes it harder to understand a workflow at a glance without inspecting all its steps. ## Proposed Solution - Add a summary field to workflows - Add specific failure reasons to the summary field on workflows - Add an LLM-generated summary of failure reason based on the job log - Add an LLM-generated summary of successfully sessions - Save the generated summary to a dedicated `summary` field on the workflow model - Expose the `summary` field via the relevant API and UI ## Acceptance Criteria - [x] A `summary` field exists on the workflow model https://gitlab.com/gitlab-org/gitlab/-/merge_requests/231554 - [x] The summary is filled with concrete errors when runners fail https://gitlab.com/gitlab-org/gitlab/-/merge_requests/232583 - [ ] An LLM-generated summary of the job logs is added to the field when it fails - [ ] An LLM-generated summary of the session is added when successful. - [x] The summary is accessible via the API https://gitlab.com/gitlab-org/gitlab/-/merge_requests/232583 - [ ] The summary is displayed in the workflow UI ## References Based on [this comment](https://gitlab.com/gitlab-org/gitlab/-/work_items/592972#note_3178446128)