[BrushGraph 4/7] Add Node UI core and simple fields

[maxmmitchell]

Description

This is the fourth PR in the Brush Graph stack. It introduces the visual infrastructure for nodes on the canvas and the simpler field editors.

Details

• Core UI for representing and interacting with nodes on-screen in NodeWidget and PortDot
• NodeRegistry maintains positons of nodes (useful for "Add node between functionality") and ports (necessary for splines snapping to ports and clean edge connection)
• UI layout data for measuring and placing ports dynamically as nodes change.
• Algorithm to layout graph nodes in a somewhat organized/pretty manner.
• Preview widgets to display brush at various stages in various shapes.
• Logic to assign tooltips to all values for various types, to be utilized in a follow-up PR.
• Logic to resolve DisplayText at UI layer.
• Expand color scheme to include necessary "Warning" shades for highlighting nodes.
• Add auto save functionality.
• Dialogs to handle all pop-up logic.
• Icon for port drag handle
• Much of the fundamental logic for the fields which will be editable in the inspector in a future PR.
• Some refactoring of code

Dependencies

• Target: brush-graph/3-viewmodel

[gemini-code-assist]

Code Review

This pull request implements the UI layer for a node-based brush behavior editor, introducing specific field editors for various node types (BinaryOp, Constant, Damping, Integral, etc.) and the core visual components for nodes and ports. The feedback focuses on critical performance optimizations within the Jetpack Compose implementation, specifically regarding the use of remember to cache expensive operations like protobuf creation and the pre-calculation of values to avoid O(N^2) complexity during recomposition or high-frequency touch events. Additionally, there are suggestions to improve maintainability by replacing magic numbers with constants and removing unused state variables.

[gemini-code-assist]

Using a magic number 1 shl 3 for tool types is brittle and hard to maintain. It should be replaced with a named constant (e.g., TOOL_TYPE_STYLUS_MASK) or derived from the InputToolType enum if possible.

[maxmmitchell]

I think this is OK, it's just for a default value and is in the proto, so very unlikely to change. We could always have a utility that treats the tooltypes as an enum and then handles the bitshifting under the hood when converting to proto, but maybe overkill. Regardless will be on a different PR since this file was moved to a follow-up PR.

[cka-dev]

Main feedback on this one is to make sure all UI composables have a modifier param,