Clarify render_preview + with_request_url behavior after 4.21.0 #2776

After upgrading from ViewComponent 4.19.0 to 4.21.0, we observed a change in URL generation when combining render_preview with with_request_url. For a component calling url_for(bar: 'baz'), rendering its preview inside with_request_url('/foo') now generates:

/rails/view_components/routing_probe_component/default?bar=baz

vc_test_request.path still returns /foo after rendering, even though the generated link points to the preview route. Replacing only render_preview with its implementation from v4.19.0 restores the previous result:

/foo?bar=baz

This appears to follow #2763, which creates an isolated preview request and replaces its controller, action, and preview path parameters before processing the action. The added test_render_preview_preserves_the_original_request_parameters covers this combination, but verifies that the original request remains unchanged rather than checking URL generation inside the preview. The documented with_request_url examples use render_inline.

Is this change in routing context intentional? Should with_request_url affect request-dependent URL generation inside render_preview? If the current behavior is intended, what is the recommended way to test request-dependent links using previews? Clarifying this interaction in the documentation would also help.