Address PR review feedback

- Change processing error response from BAD_REQUEST to INTERNAL_SERVER_ERROR
- Add "as Protobuf" to error log messages for clarity
- Add status code assertion to response validation integration test

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: jchrostek-dd

bottlecap/src/otlp/agent.rs

@@ -165,7 +165,7 @@ impl Agent {
             Err(e) => {
                 error!("OTLP | Failed to process request: {:?}", e);
                 return Self::otlp_error_response(
-                    StatusCode::BAD_REQUEST,
+                    StatusCode::INTERNAL_SERVER_ERROR,
                     format!("Failed to process request: {e}"),
                     encoding,
                 );
@@ -248,7 +248,7 @@ impl Agent {
                 };
                 let mut buf = Vec::new();
                 if let Err(e) = status.encode(&mut buf) {
-                    error!("OTLP | Failed to encode error response: {e}");
+                    error!("OTLP | Failed to encode error response as Protobuf: {e}");
                     return (status_code, [(header::CONTENT_TYPE, "text/plain")], message)
                         .into_response();
                 }
@@ -284,7 +284,7 @@ impl Agent {
             OtlpEncoding::Protobuf => {
                 let mut buf = Vec::new();
                 if let Err(e) = response.encode(&mut buf) {
-                    error!("OTLP | Failed to encode success response: {e}");
+                    error!("OTLP | Failed to encode success response as Protobuf: {e}");
                     return (
                         StatusCode::INTERNAL_SERVER_ERROR,
                         "Failed to encode response".to_string(),

integration-tests/tests/otlp.test.ts

@@ -95,7 +95,11 @@ describe('OTLP Integration Tests', () => {
     });
   });
 
-  describe('OTLP Response Validation (SVLS-8626)', () => {
+  describe('OTLP Response Validation', () => {
+    it('should invoke response validation Lambda successfully', () => {
+      expect(results.responseValidation.statusCode).toBe(200);
+    });
+
     it('should have JSON encoded span in Datadog', () => {
       const allSpans = results.responseValidation.traces?.flatMap(t => t.spans) || [];
       const hasJsonSpan = allSpans.some(s =>