test(e2e): align detached sandbox assertions

[drew]

Summary

Fix the remaining detached-main E2E assertions exposed after #2854 merged. Persistent non-interactive sandbox creation detaches before canonical-main output is streamed, so these tests now validate the resources and authorization behavior they own instead of expecting main-process stdout from the create command.

Related Issue

No issue required: localized test correction following #2854 and the failing Release Dev run https://github.com/NVIDIA/OpenShell/actions/runs/32429131484.

Changes

• Make the affected OIDC and Kubernetes sandbox creates explicitly detached.
• Remove detached main-process stdout assertions from OIDC create authorization coverage.
• Remove the same latent stdout assertions from managed and operator Kubernetes workspace coverage.
• Preserve sandbox listing, Kubernetes resource, authorization, and cleanup assertions.

Testing

• mise run pre-commit passes
• Unit tests added/updated (not applicable; E2E-only correction)
• E2E tests added/updated
• Docker OIDC PKCE can_create_sandbox tests: 4 passed, including the exact three failures from Release Dev run 32429131484
• Kubernetes managed workspace suite with CI-equivalent k3d and Helm setup: 9 passed
• Kubernetes operator workspace suite with CI-equivalent k3d and Helm setup: 5 passed
• OIDC PKCE, Kubernetes managed, and Kubernetes operator E2E test binaries compile with their required features

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (not applicable; test-only correction)