Feat: Create Neo.manager.Window for Multi-Window Geometry Tracking

Goal

Create a new core manager, Neo.manager.Window, in the App Worker to track the geometry and state of all connected browser windows. This is the foundational "God View" required for cross-window interactions like drag-and-drop.

Responsibilities

1. Registry: Maintain a collection of all connected windows, keyed by windowId.
2. Geometry Tracking: Store the screenX, screenY, outerWidth, and outerHeight for each window.
3. Updates: Provide a method (e.g., updateWindowRect(windowId, rect)) that can be called by the Main Thread (via DOM listeners or polling) to keep the worker state in sync.
4. Intersection API: Provide a method getWindowAt(screenX, screenY) that returns the windowId of the window at the given global coordinates.

Implementation Details

• Namespace: src/manager/Window.mjs
• Singleton: This should be a global singleton in the App Worker.
• Integration: It should listen for connect / disconnect events to manage the registry automatically.

Acceptance Criteria

• Neo.manager.Window exists and is accessible in the App Worker.
• It correctly tracks the list of active windows.
• (Mock/Test) Updating a window's rect updates the internal state.
• getWindowAt(x, y) correctly identifies the target window based on the stored geometry.