PrimaryPointerInfo screenCoordinates/screenDelta use bottom-left Y-up instead of top-left Y-down

Start in Explorer/Assets/DCL/SDKComponents/PrimaryPointerInfo/Systems/PrimaryPointerInfoSystem.cs at UpdatePointerInfo(), where inputPoint and Camera.Delta are assigned to ScreenCoordinates and ScreenDelta. Validate with the minimal SDK7 repro scene: the red square should stay under the cursor, and moving the mouse down should log a positive delta.y as in Bevy and Godot.

Summary

PrimaryPointerInfo.screenCoordinates and screenDelta are reported with a bottom-left origin / Y up (Unity's native screen space). Bevy and Godot report top-left origin / Y down, which is also the coordinate space of UiTransform / UiCanvasInformation. Scenes that compare the pointer against UI rects, or feed screenDelta into a VirtualCamera look, get a vertically mirrored cursor and inverted pitch on Unity only.

Where

Explorer/Assets/DCL/SDKComponents/PrimaryPointerInfo/Systems/PrimaryPointerInfoSystem.cs — UpdatePointerInfo() writes inputPoint.ReadValue<Vector2>() (Unity screen space, Y up) and the accumulated Camera.Delta straight into ScreenCoordinates / ScreenDelta.

For comparison:

• Bevy: crates/scene_runner/src/update_scene/pointer_lock.rs uses Window::cursor_position() (top-left, Y down) and the mouse-motion delta (Y down).
• Godot: lib/src/scene_runner/scene_manager.rs uses the viewport mouse position (top-left, Y down) and its frame difference.

The SDK docs specify a top-left origin with Y increasing downward, matching UiTransform. The proto comment only says "screen space (pixels)", so documenting the convention there too would help. Suggested fix: y = Screen.height - y for the position and negate delta.y.

This was reported for screenCoordinates in #8757 (closed by the stale bot, not fixed); this issue adds the screenDelta half and a repro scene.

How to validate

Minimal SDK7 scene: a 40x40 square follows the pointer using screenCoordinates in UI canvas space, and the log prints the delta sign while the pointer is locked.

import { engine, PrimaryPointerInfo, UiCanvasInformation, PointerLock } from '@dcl/sdk/ecs'
import ReactEcs, { ReactEcsRenderer, UiEntity } from '@dcl/sdk/react-ecs'
import { Color4 } from '@dcl/sdk/math'

export function main() {
  ReactEcsRenderer.setUiRenderer(() => {
    const cursor = PrimaryPointerInfo.getOrNull(engine.RootEntity)?.screenCoordinates
    const canvas = UiCanvasInformation.getOrNull(engine.RootEntity)
    if (!cursor || !canvas) return null
    return (
      <UiEntity
        uiTransform={{
          positionType: 'absolute',
          position: { left: cursor.x - 20, top: cursor.y - 20 },
          width: 40,
          height: 40,
          pointerFilter: 'none'
        }}
        uiBackground={{ color: Color4.Red() }}
      />
    )
  })

  engine.addSystem(() => {
    if (!PointerLock.getOrNull(engine.CameraEntity)?.isPointerLocked) return
    const delta = PrimaryPointerInfo.getOrNull(engine.RootEntity)?.screenDelta
    if (delta && Math.abs(delta.y) > 2) console.log(delta.y > 0 ? 'delta.y > 0' : 'delta.y < 0')
  })
}

Expected (Bevy, Godot): the red square sits under the cursor; moving the mouse down logs delta.y > 0.
Actual (Unity): the square is mirrored vertically (top of screen when the cursor is at the bottom); moving the mouse down logs delta.y < 0.