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, 5 insertions, 5 deletions

diff --git a/DomainDig/MonitoringView.swift b/DomainDig/MonitoringView.swift
index db6f685..3863e47 100644
--- a/DomainDig/MonitoringView.swift
+++ b/DomainDig/MonitoringView.swift
@@ -78,10 +78,10 @@ struct MonitoringView: View {
                                 HStack(spacing: 8) {
                                     metricBadge(title: "\(log.domainsChecked) checked")
                                     if log.changesFound > 0 {
-                                        metricBadge(title: "\(log.changesFound) changed", tint: Color(.statusWarning))
+                                        metricBadge(title: "\(log.changesFound) changed", tone: .warning)
                                     }
                                     if log.alertsTriggered > 0 {
-                                        metricBadge(title: "\(log.alertsTriggered) alerts", tint: Color(.statusCritical))
+                                        metricBadge(title: "\(log.alertsTriggered) alerts", tone: .critical)
                                     }
                                 }
                             }
@@ -100,13 +100,13 @@ struct MonitoringView: View {
         }
     }
 
-    private func metricBadge(title: String, tint: Color = Color(.statusInfo)) -> some View {
+    private func metricBadge(title: String, tone: AppStatusTone = .info) -> some View {
         Text(title)
             .font(appDensity.font(.caption2))
-            .foregroundStyle(tint)
+            .foregroundStyle(tone.foreground)
             .padding(.horizontal, 8)
             .padding(.vertical, 4)
-            .background(tint.opacity(0.16))
+            .background(tone.surface)
             .clipShape(Capsule())
     }