Validate Response against OpenAPI Schema

[giemic8]

ℹ️ This issue was partially AI-generated and may contain technical inaccuracies.

Is your feature request related to a problem? Please describe.
After importing an OpenAPI spec (#621, #835), there is no way to check whether a live response actually conforms to the documented schema, so contract drift goes unnoticed.

Describe the solution you'd like
When a request originates from (or is linked to) an imported OpenAPI operation, validate the response body/status/headers against the spec's schema and surface mismatches inline (and as assertions in a run).

Describe alternatives you've considered
Hand-writing JSON-schema assertions in scripts; validating externally with a separate tool.

Additional context
Leverages the existing OpenAPI import. Pairs with the Assertions tab (#841) and Collection Runner (#774).

[SoulKa]

@giemic8 we don't store the OpenAPI information after import. Where should this be validated? This issue needs further refinement. To keep things simple, I would also suggest to add a verify script in post-response during the import, so in OpenAPI Importer. That's a clean way without much breaking architectures.