design: white ink on any accent fill (on-accent token)

The EDIT button's armed face used on-tertiary (#0b1326 navy) on blue — the creator read it as grey
on blue and could not read it. Same problem, latent, on the armed REC/ON-AIR pills, which used the
error ink.

One rule instead of two exceptions: a saturated accent fill carries WHITE ink. New token
on-accent #ffffff, used by the EDIT trigger and RecordPillToggle; on-tertiary stays for large blue
surfaces where dark ink is right. UiShellTests pins the EDIT foreground to it.

Controls/TopBar.xaml

@@ -68,7 +68,7 @@
                         <ControlTemplate.Triggers>
                             <Trigger Property="IsChecked" Value="True">
                                 <Setter TargetName="EditBody" Property="Background" Value="{StaticResource Brush.Tertiary}"/>
-                                <Setter Property="Foreground" Value="{StaticResource Brush.OnTertiary}"/>
+                                <Setter Property="Foreground" Value="{StaticResource Brush.OnAccent}"/>
                             </Trigger>
                         </ControlTemplate.Triggers>
                     </ControlTemplate>

DESIGN.md

@@ -43,7 +43,8 @@
 | Token | Hex | Role |
 |---|---|---|
 | `tertiary` (electric blue) | `#38bdf8` | **The** interactive accent: selection, focus, sliders, primary buttons, transform handles |
-| `on-tertiary` | `#0b1326` | Text/icon on a blue fill |
+| `on-tertiary` | `#0b1326` | Dark ink, for large blue **surfaces** only |
+| `on-accent` | `#ffffff` | Text/icon on any saturated accent fill — the blue EDIT button, the armed REC/ON-AIR pills. One rule: a coloured fill carries white ink |
 | `primary` (red) | `#ff5451` | **On-air / recording only** — LIVE badge, program border, End/Go Live |
 | `primary-container` | `#b91a24` | Red pressed/hover state |
 | `secondary` (amber) | `#ffb95f` | Game audio channel, Super Chat highlight |

Themes/Controls.xaml

@@ -770,7 +770,7 @@
         <Style.Triggers>
             <Trigger Property="IsChecked" Value="True">
                 <Setter Property="Background" Value="{StaticResource Brush.Primary}"/>
-                <Setter Property="Foreground" Value="{StaticResource Brush.OnError}"/>
+                <Setter Property="Foreground" Value="{StaticResource Brush.OnAccent}"/>
             </Trigger>
         </Style.Triggers>
     </Style>

Themes/Tokens.xaml

@@ -34,6 +34,7 @@
     <!-- Accent roles: one per meaning, never mixed -->
     <SolidColorBrush x:Key="Brush.Tertiary" Color="#38bdf8"/>
     <SolidColorBrush x:Key="Brush.OnTertiary" Color="#0b1326"/>
+    <SolidColorBrush x:Key="Brush.OnAccent" Color="#ffffff"/>
     <SolidColorBrush x:Key="Brush.Primary" Color="#ff5451"/>
     <SolidColorBrush x:Key="Brush.PrimaryContainer" Color="#b91a24"/>
     <SolidColorBrush x:Key="Brush.Secondary" Color="#ffb95f"/>

ytLive.Tests/UiShellTests.cs

@@ -30,7 +30,7 @@ public class UiShellTests
         // 2. EDIT: resting face differs from the armed face, and the label follows it.
         Assert.Contains("x:Name=\"EditBody\" Background=\"{StaticResource Brush.SurfaceContainerHigh}\"", topBar);
         Assert.Contains("<Setter TargetName=\"EditBody\" Property=\"Background\" Value=\"{StaticResource Brush.Tertiary}\"/>", topBar);
-        Assert.Contains("<Setter Property=\"Foreground\" Value=\"{StaticResource Brush.OnTertiary}\"/>", topBar);
+        Assert.Contains("<Setter Property=\"Foreground\" Value=\"{StaticResource Brush.OnAccent}\"/>", topBar);
 
         // 3. Active scene = orange; live stays red.
         Assert.Contains("IsStaged}\" Value=\"True\">\n                                        <Setter Property=\"BorderBrush\" Value=\"{StaticResource Brush.Attention}\"/>", strip);