Share Lightroom's saturation bands across ours at measured strengths

Photographs opened with an earlier Lightroom edit now import its HSL
saturation as fitted against the library's own Lightroom 6 exports, rather
than one band to one band.

Measured on two looks' exports and their raws (darkroom-lrfit, hsl_map_fit),
by encoded hue: Lightroom's saturation bands act about 45 degrees either
side on our wheel, wider than ours, and not all at our strength. Each is now
shared between two or three of our bands — Aqua mostly cyan and azure, where
skies are; Blue mostly blue and violet; Orange, where skin is, at about 0.4
of its value. Values add when two of Lightroom's bands share one of ours.
On the measured skies the import now lifts muted sky blues about 1.9× against
Lightroom's 2.1×, where it gave 1.15×. Hue and luminance still go one band to
the band of the same hue; they were not measured.

ui/dr-ui/src/develop/session.rs

@@ -942,7 +942,8 @@ mod tests {
                 dr_pipeline::ParamId("blue_sat"),
             )
         };
-        assert_eq!(blue(), Some(58.0));
+        // Blue is shared across our bands at measured factors; blue takes 0.75.
+        assert_eq!(blue(), Some(58.0 * 0.75));
         assert!(!s.adopt_earlier_edit(), "taken: a second call does nothing");
         assert!(!s.graph.is_neutral());
         s.undo();