Tamarack, and the fourth character

A sixteenth theme preset, the gold larch the set was missing: nature is a green in every palette before it. It is also the first preset that costs a fourth character. Existing codes do not change.

• tamarack: gold foliage, a cold violet accent, the only occupant of the 210 to 320 hue band
• Preset index 15 encodes as u10S on base; every earlier preset keeps its three-character code