[DEV] Implement Draggable Floating Desktop Icon (macOS)

[JasonMun7]

🔨 The Task

Enable the Echo Desktop Icon (HUD) to be freely draggable across the user's screen. Currently, it is locked to a fixed position; it needs to behave like a native floating utility.

🥅 Goal

The icon is obstructing user content. We need it to behave like our other floating elements—specifically following the implementation patterns found in RecordingHud and RunHud.

📝 Implementation Details

• HUD Reference: Audit RecordingHud.swift and RunHud.swift to identify the existing window level and drag-handling logic.
• NSWindow Dragging: Implement .isMovableByWindowBackground = true or a custom mouseDragged event handler on the icon's container view.
• Coordinate Persistence: Ensure the NSWindow frame origin is saved to UserDefaults so the icon persists its position after a restart or app relaunch.
• Screen Bounds Check: Implement logic to ensure the window cannot be dragged entirely off-screen or behind the macOS Dock/Menu Bar.
• Click-Drag Separation: Ensure that dragging the HUD doesn't inadvertently trigger the "Start Workflow" action.

⚠️ Risk Level

Low
This is a window-management task. It should not impact the underlying agentic logic or the vision-processing pipeline.