* Add an OkLab gradient interpolation space and make it the new default
* Fix the Properties panel fill row resetting the gradient interpolation space to the default
* Add OkLch, Lab, LCh, and HSL gradient interpolation spaces
* Add a hue direction attribute and picker choice for polar gradient interpolation spaces
* Add an HSV gradient interpolation space
* Rename the sRGB Linear and sRGB Gamma gradient spaces to RGB Linear and RGB Gamma
* Divide the gradient interpolation dropdown between absolute and relative color spaces
* Rename the OkLch gradient interpolation space to OkLCh for channel-notation capitalization
* Shorten the color picker popover's hue direction row label to Arc
* Call the Gradient Interpolation node's parameter Space and extend the picker tooltip title to match
* Rename the gradient interpolation attribute and type family to gradient space
* Rename the gradient tool's gradient space transform to gradient to viewport transform
* Add serde aliases and a node replacement covering the gradient space renames
* Give the gradient space choices artist-facing labels and reorder the dropdown sections
* Add a Gradient Hue Direction node and its attribute read node
* Say interpolate instead of blend for gradient stop color traversal in docs and tooltips
* Label the polar perceptual gradient spaces as Perceptual Hue and group the dropdown sections by geometry
* Add a migration alias covering the gradient space attribute reader rename
* Carry the gradient hue direction attribute through boolean operations
* Register GradientHueDirection wire types in the node registry
* Add a spread method field to GradientRamp, carried at runtime as the gradient item's attribute
* Retire the Fill node's spread method input, folding its value into the gradient ramps on document upgrade
* Add an Ends spread method radio to the color picker popover, replacing the Gradient tool's control bar radio
* Update the demo art
* Rework Gradient into a newtype of List<Color> with optional position and midpoint attributes
* Fix Vello stopless-gradient fallback coverage, empty legacy gradient tables, the node docs gradient swatch, NaN position elision, and wired setter input overwrites
* Rename the node 'Length' -> 'Magnitude'
* Rename the node 'Flatten Path' -> 'Combine Paths'
* Replace the node 'Vec2 Value' with 'Combine Vec2' and add a new 'Vec2 Value' that's actually a vec2
* Update demo artwork
