feat(control-plane): idempotent deletes + command-level wiring tests

• org/project/repo delete now treat a 404 from the delete call as the desired end state (already gone), printing "<noun> <label> not found; nothing to delete" instead of surfacing a raw 404.
• Add command-level tests driving each delete command through cobra against a fake control plane: --force issues DELETE on the right path, an already-gone resource is idempotent, and a non-interactive run without --force refuses rather than deleting unprompted.

Addresses trail #642 findings.