[shivamj-del]

Issue

brev delete sends the delete request for any instance, including one that's still pending, preparing, or provisioning. The UI disables Delete in those states, because deleting mid-setup leaves the Build workflow running against an environment that no longer exists, and it then fails with "environment not found".

Fix

• Before deleting, read the environment from dev-plane (GetEnvironment added to DeleteStore) and check environment.status, the same status the UI uses.
• If it's pending, preparing, or provisioning, fail without sending the delete: instance "<name>" is still provisioning and can't be deleted yet. Run 'brev ls' and try again once it's running. The phase in the message follows the status.
• If dev-plane returns no status, fall back to the workspace status and block while it's DEPLOYING.
• New environment.SetupPhase helper next to IsFailed in pkg/environment/status.go, with a table test. Failed setups (preparing_failed, provisioning_failed) can still be deleted.