GUI: add inline colour picker control

Replace the six RGB sliders on the World tint card with a CK_COLOR control:
each row shows a live swatch and expands an inline picker with a
saturation/value square, a hue bar, and hex/RGB preview. The picker grows the
card in place so it scrolls/clips like any other row, keeps HSV state while
open (grey does not lose its hue), writes the shared 0-255 RGB triple used by
the config, and saves on mouse release.

Costs ~1.2k small rects per frame only while a picker is open; no texture
interface needed.

1 files changed, 7 insertions, 0 deletions

diff --git a/CONTEXT.md b/CONTEXT.md
index ce4a02e..b48100b 100644
--- a/CONTEXT.md
+++ b/CONTEXT.md
@@ -144,6 +144,13 @@ vocabulary / decisions.
   `x`, `y`, `category` and an `expanded` bitmask (card index order). Every
   feature now persists an `active` and `bind` pair, including movement, melee
   and spread.
+- **Colour control (`CK_COLOR`)**: row shows a live swatch; clicking the row
+  expands an inline picker (saturation/value square + hue bar + hex/RGB
+  preview) instead of three RGB sliders, growing the card in place so it
+  scrolls and clips like any other row. The picker keeps HSV state so grey
+  colours do not lose their hue; dragging writes the 0-255 RGB triple shared
+  with the config and saves on mouse release. Only one picker is open at a
+  time; closing the GUI or collapsing the card hides it.
 - Config writes are atomic: `config.tmp` is written and flushed, then
   `rename()`d over the real file. A failed write raises an error toast.