[Feature] Add GitHub Actions Workflow Support

### Is there an existing feature request for this?

- [x] I have searched the existing issues

### Describe the Feature

Enhance the existing data model by integrating GitHub Actions workflow data available via the Fivetran GitHub connector. Specifically, incorporate the `workflow`, `workflow_run`, and `workflow_pull_request` tables to provide visibility into CI/CD health and performance.

GitHub Actions is a critical part of modern software delivery, powering automated testing, deployments, and other CI/CD workflows. Despite this, the current data model does not expose any workflow-related metrics or insights.

By integrating workflow data into the model, teams can:
- Monitor workflow success/failure trends
- Identify performance bottlenecks in builds and deployments
- Correlate failing workflows with specific PRs, users, and branches
- Improve developer efficiency and reduce time to resolution for workflow-related issues

### How would you implement this feature?

Create staging models:
- stg_github__workflow
- stg_github__workflow_run
- stg_github__workflow_pull_request

Create an intermediate `int_github__workflow_summary` model. Aggregates and summarizes workflow execution activity at the repository and workflow level. Example Fields:
- repo_name
- workflow_name
- total_runs
- success_rate
- avg_duration_seconds
- failed_runs_last_7_days
- last_run_status

Finally a new end model `github__workflow_run_report` for enriched workflow run-level reporting. Joins workflow runs with pull requests and user metadata for context. This model would help support executive reporting on CI/CD health, provide insights into which PRs or branches introduce failing workflows, and drilldowns into long running or frequently failing workflows. Example Fields:
- repo_name
- workflow_name
- workflow_run_id
- status
- conclusion
- run_started_at
- duration_seconds
- pr_number
- pr_title
- pr_author

### Describe alternatives you've considered

_No response_

### Are you interested in contributing this feature?

- [ ] Yes.
- [ ] Yes, but I will need assistance.
- [ ] No.

### Anything else?

This feature would bring full visibility into a previously unmodeled but critical piece of the SDLC within GitHub: CI/CD workflows. It closes the loop from PR creation to automated testing and deployment, providing actionable insights for engineering and DevOps teams.

Commencez par localiser les modèles de données existants du connecteur GitHub ainsi que les tables sources workflow, workflow_run et workflow_pull_request. Examinez la structure des modèles de staging et intermédiaires, puis définissez le résumé de workflow et le rapport de workflow run demandés autour des champs indiqués. Le travail est terminé lorsque les trois modèles de staging, int_github__workflow_summary et github__workflow_run_report fournissent les métriques CI/CD et le contexte de pull request indiqués.

Rédigé par le modèle d'indexation à partir du texte de l'issue.