docs: remove completed refactoring documentation files

Remove refactoring plan documents that have been completed:
- e2e-config-tests-cleanup.md - Phase 1 & 2 complete
- provisioned-container-refactoring.md - Major phases complete
- domain-driven-module-organization.md - Architecture implemented
- template-renderer-separation.md - Separation implemented

These documents served their purpose during development and are no
longer needed for ongoing work. Keeping docs focused on current
and future improvements.

Author: josecelano