feat(core): add trajectoryId to ConversationOffered telemetry (#22214)

Co-authored-by: Yuna Seol <yunaseol@google.com>

packages/core/src/code_assist/server.ts

@@ -153,6 +153,7 @@ export class CodeAssistServer implements ContentGenerator {
           translatedResponse,
           streamingLatency,
           req.config?.abortSignal,
+          server.sessionId, // Use sessionId as trajectoryId
         );
 
         if (response.consumedCredits) {
@@ -223,6 +224,7 @@ export class CodeAssistServer implements ContentGenerator {
       translatedResponse,
       streamingLatency,
       req.config?.abortSignal,
+      this.sessionId, // Use sessionId as trajectoryId
     );
 
     if (response.remainingCredits) {