Adds package-info file, sets package as @NullMarked, and adds Jspecify @nullable annotation to AgentCardProducer, getEnvOrDefault Method and AgentExecutorProducer execute Method. Fixes #336

Author: ethanthopkins

tck/src/main/java/io/a2a/tck/server/AgentCardProducer.java

@@ -12,6 +12,7 @@
 import io.a2a.spec.AgentInterface;
 import io.a2a.spec.AgentSkill;
 import io.a2a.spec.TransportProtocol;
+import org.jspecify.annotations.Nullable;
 
 @ApplicationScoped
 public class AgentCardProducer {
@@ -53,7 +54,7 @@ public AgentCard agentCard() {
                 .build();
     }
 
-    private static String getEnvOrDefault(String envVar, String defaultValue) {
+    private static String getEnvOrDefault(@Nullable String envVar, String defaultValue) {
         String value = System.getenv(envVar);
         return value == null || value.isBlank() ? defaultValue : value;
     }

tck/src/main/java/io/a2a/tck/server/AgentExecutorProducer.java

@@ -4,6 +4,8 @@
 import jakarta.enterprise.context.ApplicationScoped;
 import jakarta.enterprise.inject.Produces;
 
+import org.jspecify.annotations.Nullable;
+
 import io.a2a.server.agentexecution.AgentExecutor;
 import io.a2a.server.agentexecution.RequestContext;
 import io.a2a.server.events.EventQueue;
@@ -26,7 +28,7 @@ public AgentExecutor agentExecutor() {
 
     private static class FireAndForgetAgentExecutor implements AgentExecutor {
         @Override
-        public void execute(RequestContext context, EventQueue eventQueue) throws JSONRPCError {
+        public void execute(@Nullable RequestContext context, EventQueue eventQueue) throws JSONRPCError {
             Task task = context.getTask();
 
             if (task == null) {

tck/src/main/java/io/a2a/tck/server/package-info.java

@@ -0,0 +1,10 @@
+@NullMarked
+package io.a2a.tck.server;
+
+import org.jspecify.annotations.NullMarked;
+
+//The following had @Nullable annotation applied from JSpecify
+//AgentCardProducer.java getEnvOrDefault method, 
+//AgentExecutorProducer.java execute method
+//
+