Switch to bounded elastic default scheduler.

Resolves: modelcontextprotocol#414, modelcontextprotocol#158
Replaces modelcontextprotocol#353

Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>

Author: tzolov

mcp/src/main/java/io/modelcontextprotocol/util/KeepAliveScheduler.java

@@ -141,7 +141,7 @@ public void shutdown() {
 	 */
 	public static class Builder {
 
-		private Scheduler scheduler = Schedulers.single();
+		private Scheduler scheduler = Schedulers.boundedElastic();
 
 		private Duration initialDelay = Duration.ofSeconds(0);
 
@@ -162,9 +162,9 @@ public static class Builder {
 		 * Sets the scheduler to use for executing keepAlive calls.
 		 * @param scheduler The scheduler to use:
 		 * <ul>
-		 * <li>Schedulers.single() - single-threaded scheduler (Default)</li>
-		 * <li>Schedulers.boundedElastic() - bounded elastic scheduler for I/O
-		 * operations</li>
+		 * <li>Schedulers.single() - single-threaded scheduler</li>
+		 * <li>Schedulers.boundedElastic() - bounded elastic scheduler for I/O operations
+		 * (Default)</li>
 		 * <li>Schedulers.parallel() - parallel scheduler for CPU-intensive
 		 * operations</li>
 		 * <li>Schedulers.immediate() - immediate scheduler for synchronous execution</li>