[Improve] Streamline DCG command approval (#1062)

* refactor: extract managed binary installation infrastructure

Refs #1055

* fix: address managed binary review feedback

* feat: add destructive command guard binary service

Refs #1056

* test: strengthen DCG binary service coverage

* feat: add persisted destructive command guard setting

Refs #1057

* fix: clarify DCG enablement errors

* test: cover DCG global setting schema

* feat: integrate destructive command guard with auto-approval

Closes #1058

Completes #1049

* test: document DCG auto-approval precedence

* test: raise DCG setting patch coverage

* fix: address DCG service review feedback

* fix: address managed binary review feedback

* test: cover managed binary cleanup boundaries

* fix: address DCG binary service feedback

* fix: address DCG integration feedback

* fix: finalize managed binary download handling

* test: mirror download stream close events

* test: mirror download stream close events

---------

Co-authored-by: Naved Merchant <14171946+navedmerchant@users.noreply.github.com>
Co-authored-by: edelauna <54631123+edelauna@users.noreply.github.com>