test(pipeline): MP0 - restore invariant-culture assertion dropped from formatter test

The plan's FormatReport_IsInvariantAndComplete test ends with a
DoesNotContain(",0") guard (after stripping the gc=3/1/0 token) proving
the formatter emits period decimals regardless of the host culture.
It was dropped in the Task 3 commit; restored verbatim. Passes as-is —
FormatReport already uses CultureInfo.InvariantCulture throughout.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/AcDream.App.Tests/FrameProfilerReportTests.cs

@@ -33,6 +33,7 @@ public class FrameProfilerReportTests
         Assert.Contains("alloc_kb p50=5.0 max=10.0", line);
         Assert.Contains("gc=3/1/0", line);
         Assert.Contains("upd p50=1.0", line);   // stage 0: 200µs·5 = 1.0 ms
+        Assert.DoesNotContain(",0", line.Replace("gc=3/1/0", ""));  // no comma decimals (invariant culture)
     }
 
     [Fact]