DomEvent: Fix ResizeObserver routing for external targets

When a component registers a resize listener for an external target (e.g., observing a parent node via getMonitorTargetId()), the native ResizeObserver fires on the parent node. The resulting resize event bubbles up from the parent.

Because standard DOM event routing (manager/DomEvent.mjs) iterates the upward bubbling path and checks the listener maps of the components in that path, it never finds the listener registered by the child component, creating a routing black hole where the event is dropped.

This ticket refactors the architecture to decouple resize event routing from DOM bubbling entirely:

• manager/DomEvent now sends both the component.id and the targetId to the Main Thread when registering the observer.
• main.addon.ResizeObserver maintains a Map of targetId -> [componentIds], tracking exactly which App Worker components requested the observation.
• The Main Thread includes the explicit componentIds array in the resize event payload.
• manager/DomEvent intercepts the resize event, bypasses normal bubbling, and directly routes the event to the explicit mailboxes of the registered components.
• Ensures disabled components still receive resize events to maintain correct layout geometry.

This fixes the desktop resize regression in HeaderCanvas and establishes a reliable, explicit routing mechanism for cross-node observations.