feat: update ConfigAgentLoader to load agents from the current directory

The ConfigAgentLoader is updated to support loading agent configurations directly from the specified directory, in addition to subdirectories. This allows for more flexible project structures where an agent configuration might reside alongside a pom.xml without needing its own subdirectory.

PiperOrigin-RevId: 800650807

Author: Doris26

maven_plugin/examples/simple-agent/pom.xml

@@ -62,4 +62,4 @@
             </plugin>
         </plugins>
     </build>
-</project>
+</project>

maven_plugin/src/main/java/com/google/adk/maven/ConfigAgentLoader.java

@@ -140,6 +140,25 @@ private void discoverAgents() throws IOException {
 
     logger.info("Initial scan for YAML agents in: {}", sourcePath);
 
+    // First, check if the current directory itself contains a root_agent.yaml
+    Path currentDirYamlPath = sourcePath.resolve(YAML_CONFIG_FILENAME);
+    if (Files.exists(currentDirYamlPath) && Files.isRegularFile(currentDirYamlPath)) {
+      String agentName = sourcePath.getFileName().toString();
+      logger.debug("Discovering YAML agent config in current directory: {}", currentDirYamlPath);
+
+      // Create a memoized supplier that will load the agent only when requested
+      agentSuppliers.put(agentName, Suppliers.memoize(() -> loadAgentFromPath(currentDirYamlPath)));
+
+      // Register with watcher if hot-reloading is enabled
+      if (hotReloadingEnabled && watcher != null) {
+        watcher.watch(sourcePath, agentDirPath -> updateAgentSupplier(agentDirPath));
+      }
+
+      logger.info("Discovered YAML agent '{}' from: {}", agentName, currentDirYamlPath);
+      return;
+    }
+
+    // Otherwise, scan subdirectories for agents
     try (Stream<Path> entries = Files.list(sourcePath)) {
       for (Path agentDir : entries.collect(toList())) {
         if (Files.isDirectory(agentDir)) {