Add crates/qbz-ui/ui/primitives/ColorPicker.slint: a self-contained inline
HSV picker (no PopupWindow, so no z-order/positioning fight). A saturation/
value square (pure-hue base + white->transparent + transparent->black
overlays, draggable crosshair), a 7-stop hue strip with a draggable marker,
a live preview swatch, and an editable #rrggbb HEX field.
The picker owns its hue/sat/val so dragging s or v to an edge never loses the
hue; it seeds from `value` on mount and on external changes, guarded by a
`dragging` flag so the round-tripped color the parent feeds back mid-drag does
not fight the crosshair. HSV->RGB uses Colors.hsv; RGB->HSV and int->hex are
self-contained pure functions (Slint has no local bindings, so intermediates
are derived helper properties). Hex parsing is delegated to the parent via
`hex-committed` (Slint cannot parse a hex string). Emits `changed(color)` live
on every drag frame. Validated with the slintcheck stub.
cc
vicrodh
2001a40486