Vamooses Dye Studio

**Added**
- Dye-channel coverage: each dyeable decor now shows, per channel, how much of
  its surface that channel covers and what part it dyes. Canvas and Live mode
  display it as a readout on each channel -- "Part - Material - NN%", for
  example "Gilt frame & basin - Gilt - 65%". Built from the decor models'
  dye masks, covering 180 decor.
- Harmonise is now area-aware. It places the lead colour on the largest surface
  and the supporting colours on the smaller ones, so the result reads as a
  balanced scheme rather than three unrelated dyes.
- "Apply all" harmonise mode (toggle): re-dyes every channel from one starter
  dye you pick, balanced by surface area, instead of filling only the other
  channels. The toggle is in the Canvas harmonise menu, the Live edit header,
  and the settings sidebar.
- Live mode's gallery tiles show a small corner colour chip, tinted to the
  area-weighted average of the decor's applied dyes.