fix(traces): suppress clippy cast_possible_truncation for u128→u64 trace IDs

The truncation is intentional — Datadog protocol transmits the lower
64 bits via x-datadog-trace-id, with upper bits in _dd.p.tid tag.

Author: duncanista

bottlecap/src/lifecycle/invocation/processor.rs

@@ -980,7 +980,10 @@ impl Processor {
 
         // Set the extracted trace context to the spans
         if let Some(sc) = &context.extracted_span_context {
-            context.invocation_span.trace_id = sc.trace_id as u64;
+            #[allow(clippy::cast_possible_truncation)] // Datadog protocol uses lower 64 bits
+            {
+                context.invocation_span.trace_id = sc.trace_id as u64;
+            }
             context.invocation_span.parent_id = sc.span_id;
 
             // Set the right data to the correct root level span,
@@ -1210,7 +1213,10 @@ impl Processor {
         // If we have a trace context, this means we got it from
         // distributed tracing
         if let Some(sc) = &context.extracted_span_context {
-            trace_id = sc.trace_id as u64;
+            #[allow(clippy::cast_possible_truncation)] // Datadog protocol uses lower 64 bits
+            {
+                trace_id = sc.trace_id as u64;
+            }
             parent_id = sc.span_id;
             tags.extend(sc.tags.clone());
         }

bottlecap/src/lifecycle/listener.rs

@@ -218,10 +218,14 @@ impl Listener {
     fn inject_span_context_to_headers(headers: &mut HeaderMap, span_context: &SpanContext) {
         headers.insert(
             DATADOG_TRACE_ID_KEY,
-            (span_context.trace_id as u64)
-                .to_string()
-                .parse()
-                .expect("Failed to parse trace id"),
+            {
+                #[allow(clippy::cast_possible_truncation)] // Datadog protocol uses lower 64 bits
+                let trace_id = span_context.trace_id as u64;
+                trace_id
+            }
+            .to_string()
+            .parse()
+            .expect("Failed to parse trace id"),
         );
 
         if let Some(priority) = span_context.sampling.priority {