[REFACTOR] Updater, signing, and release promotion

[ksamaschke]

Scoped Behavior Slice

Improve structure, naming, and maintainability for 'Updater, signing, and release promotion' without changing externally verified behavior.

Test Command or Verification Path

• Re-run the scoped GREEN verification after cleanup.
• Run the relevant regression suite to confirm no behavior changed.

Required Evidence Format

• Link passing evidence back to the GREEN work-item.
• Capture passing regression or suite evidence after refactor cleanup.

Tracking

• Type: work-item
• Phase: refactor

Parent: #182

[ksamaschke]

Completed as part of merged story #182 in PR #197 (merge commit , implementation commit ). The refactor/cleanup phase is already represented by the merged release-flow validation and operator documentation updates. Closing stale TDD child issue.

[ksamaschke]

Completed as part of merged story #182 in PR #197 (merge commit 9f8cebb, implementation commit c1f2436). The refactor/cleanup phase is already represented by the merged release-flow validation and operator documentation updates. Closing stale TDD child issue.