audit(#622): sweep hardcoded colors + add checkColorLiterals guard (#626)

Removed docs/color-hardcoded-audit.md per request. Replaced 2 hardcoded
Color literals with theme tokens; added CI guard blocking new literals.

Co-authored-by: Hy4ri <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/ui/chat/ChatBubble.kt

@@ -1886,7 +1886,7 @@ private fun ToolBubble(
     var expanded by remember { mutableStateOf(false) }
     var showRawJson by remember { mutableStateOf(false) }
     val chipColor = if (isDarkTheme) ToolChipColor else ToolChipColorLight
-    val contentColor = if (isDarkTheme) Color.White else Color.Black
+    val contentColor = MaterialTheme.colorScheme.onSurfaceVariant
     val statusColors = LocalHermesStatusColors.current
 
     val parsed =