Silverstripe Version Upgrade Skill

Repeatable workflow for upgrading Silverstripe CMS projects (e.g. SS4 → SS5) in Dynamic Agency's module ecosystem and DDEV-based local development.

Upgrade Phases (Summary)

Phase	Key Actions
1. Assessment	Audit versions, packages, incompatibilities; clone legacy instance for VR baseline
2. Branch & PHP	Create feature branch, update PHP to `^8.1`
3. Dependencies	Update recipes with `--no-update`, resolve, `vendor-expose`
4. Config Migration	Fix extension relocations, ORM relationships, templates
5. Data Migration	Write idempotent BuildTasks for link/data migrations
6. Build & Verify	`dev/build`, run tasks, check frontend + CMS
7. Code Quality	PHPCS, PHPStan, annotation fixes
8. Commit & PR	Conventional commit, checklist PR body
9. UAT	Deploy, run tasks, verify, troubleshoot
10. Production	Merge, deploy, run tasks, verify