[Icons] Author icon emphasis colors as palette roles

The emphasis levels were computed from the accent at paint time, so a
theme could not vary them: every theme got the same derived strong and
soft tones, and a semantic hue was pushed toward the accent whether the
author wanted that or not.

Give each family three authored roles instead. Icon/IconStrong/IconSoft
carry the neutral glyph ink and Positive/Negative gain the same Strong
and Soft companions. Emphasis becomes a lookup inside the family, and a
caller that names a variant pins that level at every emphasis. The paint
path returns the authored color verbatim; only the filled treatments keep
their saturation floor, because carrying a disc or a fill is a treatment
decision.

Shipped palettes author the full ladder for both schemes; the palette
editor exposes the new rows and the generator writes them. System keeps
deriving its neutral ink from the platform palette, since it ships no
palette of its own.

cockatrice/themes/Leather/palette-default-dark.toml

@@ -71,6 +71,13 @@ Accent               = #c9995a
 [AppColors]
 AccentStrong         = #b7823b
 AccentSoft           = #e4c58f
+Icon                 = #bc8c4a
+IconStrong           = #d4b68c
+IconSoft             = #86745a
 Positive             = #6dd58c
+PositiveStrong       = #99e2ae
+PositiveSoft         = #588061
 Negative             = #ff8a80
+NegativeStrong       = #ffada6
+NegativeSoft         = #996b66
 

cockatrice/themes/Leather/palette-default-light.toml

@@ -71,6 +71,13 @@ Accent               = #a5712f
 [AppColors]
 AccentStrong         = #b7823b
 AccentSoft           = #e4c58f
+Icon                 = #735125
+IconStrong           = #4e3719
+IconSoft             = #817059
 Positive             = #1b7f3b
+PositiveStrong       = #0f4520
+PositiveSoft         = #61795d
 Negative             = #b3261e
+NegativeStrong       = #741914
+NegativeSoft         = #9a665b