Router: Destroy route component when disconnected (Fixes #21272)

[nielslyngsoe]

Fixes #21272

Test Notes:

Notice this will destroy a route component when the router element is disconnected. Is there any case where we like to reuse an element despite the router being removed? Or is there a case where a router gets disconnected and reconnected, so the destroy would result in breaking the content of the router?

[Copilot]

Pull request overview

This PR fixes issue #21272 by ensuring route components are properly destroyed when a router element is disconnected from the DOM. The changes add cleanup logic to prevent memory leaks and ensure proper lifecycle management of routed components.

Key changes:

• Added cleanup in router-slot's disconnectedCallback to clear children and reset route match state
• Applied umbDestroyOnDisconnect directive to workspace elements in modals to ensure proper destruction

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Umbraco.Web.UI.Client/src/packages/core/router/router-slot/router-slot.ts	Adds clearChildren() and _routeMatch = null to disconnectedCallback to properly destroy child route components when router is disconnected
src/Umbraco.Web.UI.Client/src/packages/core/workspace/modals/workspace-modal.element.ts	Applies umbDestroyOnDisconnect() directive to workspace elements to ensure proper cleanup when modal is closed