Add route mount precondition assertions to version pinning specs

What does this MR do and why?

Adds route precondition assertions (expect(router.currentRoute.name).toBe(...)) to the Edit page and Duplicate page sections of flow_version_pinning_integration_spec.js and agent_version_pinning_integration_spec.js so tests verify they mounted on the intended route rather than silently falling back to DEFAULT_ROUTE.

References

• Closes #595220
• Follow-up from !228732 (merged)

How to set up and validate locally

yarn jest ee/spec/frontend/ai/catalog/integration/flow_version_pinning_integration_spec.js ee/spec/frontend/ai/catalog/integration/agent_version_pinning_integration_spec.js

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist.