Agent Config Changes modified as per adk python

[chhitiz-t]

Feature: Configuration Agent Loading Refactor & Hot-Reload

This Pull Request introduces a significant refactoring of the configuration-based agent loading system to strictly align with established Python ADK patterns. The primary goals are to enhance extensibility, optimize resource usage, and add crucial hot-reloading support for configuration changes.

Key Architectural Changes

| AgentLoader (Interface) | dev/web | Extended interface for better cache management and resource cleanup. |
| ConfigAgentLoader | maven_plugin | New, complete configuration-based implementation handling hot-reloading and lazy access. |
| ConfigAgentWatcher | maven_plugin | Dedicated file watcher for monitoring configuration directory changes. |

-- Detailed Changes and Improvements

1. AgentLoader Interface Enhancements

The base interface has been extended to support crucial cache management and lifecycle methods, inspired by the Python ADK:

• hasAgent(String name): Checks for agent existence (default implementation provided).
• removeAgentFromCache(String name): Removes a specific agent instance, forcing a reload on next access (aligned with Python ADK cache invalidation).
• stop(): Provides a cleanup mechanism for resources (e.g., stopping the file watcher).

2. ConfigAgentLoader Implementation

This is the core new class, implementing robust configuration loading:

• Hot-Reloading Support: Automatically detects changes in YAML files, ensuring agents are reloaded dynamically without a service restart.
• Performance: Implements Lazy Loading with Memoization—agents are loaded and initialized only upon their first request and then cached.
• Cache Management API: Provides methods for granular control:
  • removeAgentFromCache()
  • forceReload()
  • forceReloadAll()
• Reload Callbacks: Introduces setOnAgentsReloadedCallback() to notify external systems when configurations are reloaded (mirroring the Python ADK's runners_to_clean pattern).
• Extensibility: Uses protected methods allowing subclasses to easily override default behavior for agent discovery, loading logic, and watcher configuration.
• Robustness: Includes tracking for agents that fail to load, preventing repeated loading attempts.

3. ConfigAgentWatcher (New Component)

This new thread-safe utility manages filesystem monitoring:

• Configuration Monitoring: Recursively scans configured agent directories for files ending in .yaml or .yml.
• Polling: Operates on a dedicated, daemon polling thread at configurable intervals (default: 2 seconds).
• Change Detection: Efficiently detects new, modified, and deleted configuration files.
• Extensibility: Protected methods allow for custom overriding of directory scanning and file detection logic.

Design Inspiration

This refactoring strictly adheres to established patterns from the Python ADK, specifically:

• AgentLoader and Cache Invalidation: The core loading logic and removeAgentFromCache method.
• agent_change_handler.py: The inspiration for the file watching, thread management, and the setOnAgentsReloadedCallback notification system.
• Extensibility: Architected around inheritance and protected methods to simplify future customization and extension.