fix: resolve resSchema namespace for shared response schemas

[arlindaxhemailii]

When a response schema is shared across multiple tags, the resolver correctly assigns it to the default (Common) namespace. However, passing the endpoint tag as namespaceTag to getImportedZodSchemaName bypassed this resolution logic and forced the schema into the endpoint's namespace.

As a result, shared schemas such as StatusResponseSchema were emitted as:

• RocketsModels.StatusResponseSchema

instead of:

• CommonModels.StatusResponseSchema

This left resSchema undefined at runtime, causing successful responses to fail validation and surface as openapi.sharedErrors.unknownError.

This fixes the regression introduced in 3.0.0 by removing the namespaceTag override for response schemas and restoring automatic namespace resolution through getTagByZodSchemaName.

Also adds regression tests covering both resolution paths:

• Shared schema used across multiple tags → CommonModels
• Schema owned by a single tag → owning tag namespace (RocketsModels)