feat: SG-41316: Add Dissolve blend composite mode to stackIPNode with UI controls

[nigelsumner]

Add dissolve blend composite mode with UI controls

This PR implements a new dissolve blend composite mode for OpenRV's stack compositor with full UI integration and real-time controls.

OpenRV_dissolveBlend.mov

Features Added

• ✅ Dissolve blend mode in StackIPNode for 2-input compositing
• ✅ GPU shader implementation (Dissolve2.glsl) with configurable amount
• ✅ UI slider and text input controls in Session Manager
• ✅ Real-time dissolve amount adjustment (0.0 to 1.0 range)
• ✅ Immediate UI updates when switching between composite modes

Technical Implementation

Core Implementation

• StackIPNode.cpp: Added dissolve mode support with m_dissolveAmount property
• StackIPNode.h: Added property declaration for dissolve amount control
• ShaderCommon.cpp/.h: Implemented newDissolveBlend() function for GPU shader management

GPU Shaders

• Dissolve2.glsl: GLSL shader for hardware-accelerated dissolve blending

UI Integration

• composite.ui: Added QSlider and QLineEdit controls for dissolve amount
• Composite_edit_mode.mu: Enhanced with slider integration and UI synchronization

Build System

• CMakeLists.txt: Updated build configuration for dissolve shader compilation

Testing

• ✅ Successfully builds on macOS with existing OpenRV build system
• ✅ UI controls properly show/hide when switching composite modes
• ✅ Slider and text field remain synchronized during interaction
• ✅ Dissolve blending works correctly with 2-input stacks

Usage

1. Load two media sources into a stack
2. In Session Manager, set composite mode to "Dissolve"
3. Use the slider or text input to control dissolve amount (0.0 = first input, 1.0 = second input)
4. Real-time preview updates as you adjust the dissolve amount

[pbergeron-adsk]

This looks OK to me, needs to be view tested.

[bernie-laberge]

Thank you @nigelsumner for this great contribution !

[cedrik-fuoco-adsk]

Hi @nigelsumner,

Thank you for the contribution! Could you fix the pre-commit issue? You might have to run the pre-commit manually on the files you modified.

[nigelsumner]

Hey Cedrik, apologies for the messy commits. I'm still learning my way around the nuances of github. I figured a clean and rebase was the easiest fix. Still so much to learn on this platform. Cheers.

[cedrik-fuoco-adsk]

It's ok, no problem! We will be testing your PR soon. Thank you for your contribution!