Replace assert with conditional for to_chars error handling

assert is compiled out in release builds, so handle the error
by silently skipping the ksr tag instead.

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

Author: bm1549

src/datadog/trace_segment.cpp

@@ -331,8 +331,10 @@ void TraceSegment::make_sampling_decision_if_null() {
     const auto [ptr, ec] = std::to_chars(buf.data(), buf.data() + buf.size(),
                                          *sampling_decision_->configured_rate,
                                          std::chars_format::general, 6);
-    assert(ec == std::errc());
-    trace_tags_.emplace_back(tags::internal::ksr, std::string(buf.data(), ptr));
+    if (ec == std::errc()) {
+      trace_tags_.emplace_back(tags::internal::ksr,
+                               std::string(buf.data(), ptr));
+    }
   }
 }