fix(cli): reuse sandbox provisioning display

[sjenning]

Summary

Fix the interactive provisioning display across platform progress events during openshell sandbox create. This prevents repeated events from recreating the display and duplicating or discarding rendered progress steps.

Regression introduced by #1989

Before:

$ openshell sandbox create
Created sandbox: regular-ribbonfish
✓ Sandbox allocated (2s)
✓ Sandbox allocated (2s)
✓ Sandbox allocated (2s)
✓ Sandbox allocated (2s)
✓ Sandbox allocated (2s)
✓ Sandbox allocated (2s)
✓ Sandbox allocated (2s)
✓ Sandbox allocated (2s)
✓ Sandbox allocated (2s)
✓ Sandbox allocated (2s)
✓ Sandbox allocated (2s)
✓ Sandbox allocated (2s)
✓ Sandbox allocated (2s)
✓ Sandbox allocated (2s)
✓ Sandbox allocated (2s)
1000780000@default--regular-ribbonfish:/sandbox$

After

$ openshell sandbox create
Created sandbox: punctual-saury
1000780000@default--punctual-saury:~$

Related Issue

No issue required: this is an obvious localized CLI rendering bug fix.

Changes

• Borrow the existing interactive ProvisioningDisplay while handling platform progress events
• Keep plain progress output behavior unchanged
• Add a regression test proving repeated events reuse one display without duplicate completed steps

Testing

• mise run pre-commit passes
• Unit tests added/updated
• E2E tests added/updated (not applicable; no sandbox infrastructure or protocol behavior changed)
• cargo test -p openshell-cli platform_progress_events_update_borrowed_display_without_duplicate_steps

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (not applicable; implementation-only rendering fix)

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[drew]

Thanks!

[drew]

/ok to test 4aa6c27