Test - Add unit tests for thresholding operators #141
Description
Is your feature request related to a problem?
The thresholding operators (ApplyThreshold, AdaptiveThreshold, OtsuThreshold) have no unit tests. This means regressions in their behaviour, such as incorrect default values, wrong output dtype, or broken grayscale/RGBA handling cannot be caught automatically.
Describe the solution you'd like
Add a unit test suite covering all three thresholding operators, including shape and dtype assertions, binary output verification, grayscale and RGBA input handling, default parameter behaviour, and the existing maxValue=0 bug in ApplyThreshold.