[isrcalebe]

Overview

Adds headless tests covering the presence and sizing behaviour of MsdfSpriteText.

The tests verify that the drawable follows the expected SpriteText semantics when its text changes, including the interaction between IsPresent, auto-sizing and AlwaysPresent behaviour.

Changes

• add headless tests for MsdfSpriteText.IsPresent
• verify that an empty text makes the drawable not present
• verify that auto-sized containers collapse correctly when the text becomes empty
• verify that AlwaysPresent subclasses remain present with empty text
• verify the expected sizing behaviour before and after clearing the text
• add a flow test to ensure presence state remains stable during layout/update processing

These tests are intended to ensure that MsdfSpriteText behaves consistently with the existing SpriteText lifecycle and container layout semantics.