Merge CB-577 follow-up: drop the target-keyed async index

asyncTasksByWaiter correlates an async question by the exact rendezvous
waiter, so the target-keyed set it replaced can no longer decide
anything. Keeping it meant two indexes of the same fact, one of them
ambiguous whenever a target has two accepted tickets.

The race the old test modelled by reflection is gone with it: identity
keys make 'some other task reached this target' unrepresentable, so
there is no longer a wrong task for the question to land on.

Also carries the criterion-1 doc correction, which is identical to
aac29d6 on a different parent.

bridged/src/main/java/dev/ltms/bridged/msg/MessageService.java

@@ -9,7 +9,6 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.util.List;
-import java.util.Set;
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionException;
@@ -171,8 +170,6 @@ public final class MessageService {
     private final Metrics metrics; // CB-502: nullable — no registry in unit tests
     private final ConcurrentHashMap<String, ReentrantLock> sessionLocks = new ConcurrentHashMap<>();
     private final ConcurrentHashMap<String, Task> tasks = new ConcurrentHashMap<>();
-    /** Async tasks that have accepted delivery for a target. */
-    private final ConcurrentHashMap<String, Set<Task>> asyncTasksByTarget = new ConcurrentHashMap<>();
     /** Async task that owns each exact forward rendezvous waiter. */
     private final ConcurrentHashMap<CompletableFuture<Rendezvous.Resolution>, Task> asyncTasksByWaiter =
             new ConcurrentHashMap<>();
@@ -548,13 +545,7 @@ public final class MessageService {
         tasks.put(ticket, task);
         asyncExecutor.submit(() -> {
             try {
-                Runnable trackingAccepted = () -> {
-                    if (onAccepted != null) {
-                        onAccepted.run();
-                    }
-                    asyncTasksByTarget.computeIfAbsent(target, _ -> ConcurrentHashMap.newKeySet()).add(task);
-                };
-                Reply result = send(target, content, ASYNC_TIMEOUT_MS, trackingAccepted, task);
+                Reply result = send(target, content, ASYNC_TIMEOUT_MS, onAccepted, task);
                 if (result.outcome() == Outcome.QUESTION) {
                     // Keep the accepted owner until answer() finishes it. markAsyncQuestion may run
                     // just after resolveQuestion wakes this thread.
@@ -563,7 +554,6 @@ public final class MessageService {
                 }
             } catch (Throwable t) {
                 task.future.completeExceptionally(t);
-                untrackAsyncTarget(task);
             }
         });
         pruneTerminalTickets();
@@ -643,7 +633,6 @@ public final class MessageService {
             if (forgetTurn) {
                 asyncTasksByTurn.remove(turnId, task);
                 task.turnId = null;
-                untrackAsyncTarget(task);
             }
         }
     }
@@ -651,7 +640,6 @@ public final class MessageService {
     /** Complete and detach an async ticket after its worker's actual terminal reply. */
     private void finishAsyncTask(Task task, Reply result) {
         task.future.complete(result);
-        untrackAsyncTarget(task);
         if (task.turnId != null) {
             asyncTasksByTurn.remove(task.turnId, task);
         }
@@ -670,17 +658,6 @@ public final class MessageService {
         return asyncTasksByTurn.values().stream().anyMatch(task -> target.equals(task.target));
     }
 
-    /** Stop tracking a task once it no longer owns an accepted target turn. */
-    private void untrackAsyncTarget(Task task) {
-        Set<Task> targetTasks = asyncTasksByTarget.get(task.target);
-        if (targetTasks != null) {
-            targetTasks.remove(task);
-            if (targetTasks.isEmpty()) {
-                asyncTasksByTarget.remove(task.target, targetTasks);
-            }
-        }
-    }
-
     /** Release the async executor. */
     public void close() {
         asyncExecutor.shutdown();