Regression: Store.load({url}) fails when Store has no initial URL config

Goal

Restore the ability for Store.load({ url: '...' }) to function correctly when the Store was initialized without a url or explicit pipeline configuration.

Context

In the recent data layer refactoring (moving toward explicit Pipelines), we introduced a regression. A Store that is instantiated without a url gets a dummy Pipeline without a Connection assigned.

When a dynamic URL is later passed directly to store.load({ url: 'data.json' }), the Pipeline attempts to read from a missing connection (me.pipeline.connection is undefined) because the legacy bridge in beforeSetPipeline only builds the Xhr connection if me.url is set during initialization.

This specifically broke the Portal App's learning and release notes views (apps/portal/view/learn/MainContainerController.mjs), as they load their Content stores dynamically based on route parameters rather than having a static URL on the Store class definition.

Acceptance Criteria

1. Update Store.load() to check if opts.url is present but the pipeline lacks a connection.
2. If so, dynamically import and assign a Neo.data.connection.Xhr instance to the pipeline just-in-time, using the provided URL.
3. Ensure this logic executes correctly before await me.pipeline.read(params).
4. Create a new unit test test/playwright/unit/data/StoreDynamicUrl.spec.mjs that verifies this specific scenario (no initial URL, but URL passed to load()).