fix: use invariant culture in numeric display formatting (#158)

* fix: use invariant culture in token and cost display formatting

FormatLargeNumber and CostUsd were using the current thread culture,
producing "2,5M" or "$0,25" on non-English locales instead of the
expected "2.5M" / "$0.25".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* test: add regression for invariant culture numeric formatting

Covers non-English culture formatting so token and cost display stays
as 2.5M / .25 rather than locale-specific 2,5M / ,25.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: AlexAlves87 <alexalves87@github.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: Scott Hanselman <scott@hanselman.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: 5 people

src/OpenClaw.Shared/Models.cs

@@ -1,3 +1,5 @@
+using System.Globalization;
+
 namespace OpenClaw.Shared;
 
 public enum ConnectionStatus
@@ -295,7 +297,7 @@ public string DisplayText
             if (TotalTokens > 0)
                 parts.Add($"Tokens: {ModelFormatting.FormatLargeNumber(TotalTokens)}");
             if (CostUsd > 0)
-                parts.Add($"${CostUsd:F2}");
+                parts.Add("$" + CostUsd.ToString("F2", CultureInfo.InvariantCulture));
             if (RequestCount > 0)
                 parts.Add($"{RequestCount} requests");
             if (!string.IsNullOrEmpty(Model))
@@ -455,8 +457,8 @@ internal static class ModelFormatting
     /// </summary>
     internal static string FormatLargeNumber(long n)
     {
-        if (n >= 1_000_000) return $"{n / 1_000_000.0:F1}M";
-        if (n >= 1_000) return $"{n / 1_000.0:F1}K";
+        if (n >= 1_000_000) return (n / 1_000_000.0).ToString("F1", CultureInfo.InvariantCulture) + "M";
+        if (n >= 1_000) return (n / 1_000.0).ToString("F1", CultureInfo.InvariantCulture) + "K";
         return n.ToString();
     }
 }

tests/OpenClaw.Shared.Tests/ModelsTests.cs

@@ -1,3 +1,4 @@
+using System.Globalization;
 using Xunit;
 using OpenClaw.Shared;
 
@@ -541,6 +542,37 @@ public void DisplayText_CombinesAllFields_WhenAllPresent()
         Assert.Contains("25 requests", display);
         Assert.Contains("gpt-4", display);
     }
+
+    [Fact]
+    public void DisplayText_UsesInvariantCulture_ForTokenAndCostFormatting()
+    {
+        var originalCulture = CultureInfo.CurrentCulture;
+        var originalUiCulture = CultureInfo.CurrentUICulture;
+
+        try
+        {
+            CultureInfo.CurrentCulture = new CultureInfo("fr-FR");
+            CultureInfo.CurrentUICulture = new CultureInfo("fr-FR");
+
+            var usage = new GatewayUsageInfo
+            {
+                TotalTokens = 2_500_000,
+                CostUsd = 0.25
+            };
+
+            var display = usage.DisplayText;
+
+            Assert.Contains("2.5M", display);
+            Assert.Contains("$0.25", display);
+            Assert.DoesNotContain("2,5M", display);
+            Assert.DoesNotContain("$0,25", display);
+        }
+        finally
+        {
+            CultureInfo.CurrentCulture = originalCulture;
+            CultureInfo.CurrentUICulture = originalUiCulture;
+        }
+    }
 }
 
 public class GatewayNodeInfoTests