fix(a11y): rebalance the light palette so hues survive

Reported as "colors seem muted and hard to see on light mode", and
correct. The light palette optimised contrast and produced mud: #7A5600
reads olive rather than amber, #146C2E bottle-dark rather than green.
Contrast passed while the UI got harder to read, because hue identity is
what distinguishes warning from critical at a glance.

Two causes, both fixed.

Every foreground was required to clear 4.5:1 against its own 16% badge
tint — the harshest surface it ever sits on — which pushed each colour
about 20% darker than the common case needed. Most of what is actually on
screen is plain text on a card, with far more headroom. The fill is now
decoupled from the foreground: AppStatusTone carries a foreground and a
surface authored independently, with matching …Surface colorsets, so a
foreground no longer has to survive a wash of itself. Every status
foreground is now fully saturated.

And warning was yellow. Yellow cannot stay yellow at a lightness low
enough to pass 4.5:1 on white — it becomes olive. That is colorimetric,
not a tuning problem. Warning is now orange: #AD5100 light, #FF9F0A dark.

New light values: positive #008035, warning #AD5100, critical #CC0700.
Worst-case ratios 4.54–6.76 across page, card, and surface in both
schemes. Audit findings are unchanged — light 21, dark 18 — so the
vividness costs nothing.

Also picks up a literal .blue missed in phase 1: DomainDiffItem's
low-severity change colour, which the phase 1 sweep did not cover because
its pattern listed only cyan/yellow/green/red/orange/pink.

1 files changed, 78 insertions, 0 deletions

diff --git a/Shared/Colors.xcassets/StatusPositiveSurface.colorset/Contents.json b/Shared/Colors.xcassets/StatusPositiveSurface.colorset/Contents.json
new file mode 100644
index 0000000..dc80f8f
--- /dev/null
+++ b/Shared/Colors.xcassets/StatusPositiveSurface.colorset/Contents.json
@@ -0,0 +1,78 @@
+{
+  "colors": [
+    {
+      "idiom": "universal",
+      "color": {
+        "color-space": "srgb",
+        "components": {
+          "red": "0xE3",
+          "green": "0xF7",
+          "blue": "0xEC",
+          "alpha": "1.000"
+        }
+      }
+    },
+    {
+      "idiom": "universal",
+      "appearances": [
+        {
+          "appearance": "luminosity",
+          "value": "dark"
+        }
+      ],
+      "color": {
+        "color-space": "srgb",
+        "components": {
+          "red": "0x0E",
+          "green": "0x2A",
+          "blue": "0x18",
+          "alpha": "1.000"
+        }
+      }
+    },
+    {
+      "idiom": "universal",
+      "appearances": [
+        {
+          "appearance": "contrast",
+          "value": "high"
+        }
+      ],
+      "color": {
+        "color-space": "srgb",
+        "components": {
+          "red": "0xD3",
+          "green": "0xF0",
+          "blue": "0xE0",
+          "alpha": "1.000"
+        }
+      }
+    },
+    {
+      "idiom": "universal",
+      "appearances": [
+        {
+          "appearance": "luminosity",
+          "value": "dark"
+        },
+        {
+          "appearance": "contrast",
+          "value": "high"
+        }
+      ],
+      "color": {
+        "color-space": "srgb",
+        "components": {
+          "red": "0x12",
+          "green": "0x3A",
+          "blue": "0x20",
+          "alpha": "1.000"
+        }
+      }
+    }
+  ],
+  "info": {
+    "author": "xcode",
+    "version": 1
+  }
+}