refactor: consolidate debug logging across tools with shared DebugSession class

- Introduced a new DebugSession class in tools/debug_helpers.py to centralize debug logging functionality, replacing duplicated code across various tool modules.
- Updated image_generation_tool.py, mixture_of_agents_tool.py, vision_tools.py, web_tools.py, and others to utilize the new DebugSession for logging tool calls and saving debug logs.
- Enhanced maintainability and consistency in debug logging practices across the codebase.

tools/openrouter_client.py

@@ -0,0 +1,34 @@
+"""Shared OpenRouter API client for Hermes tools.
+
+Provides a single lazy-initialized AsyncOpenAI client that all tool modules
+can share, eliminating the duplicated _get_openrouter_client() / 
+_get_summarizer_client() pattern previously copy-pasted across web_tools,
+vision_tools, mixture_of_agents_tool, and session_search_tool.
+"""
+
+import os
+
+from openai import AsyncOpenAI
+from hermes_constants import OPENROUTER_BASE_URL
+
+_client: AsyncOpenAI | None = None
+
+
+def get_async_client() -> AsyncOpenAI:
+    """Return a shared AsyncOpenAI client pointed at OpenRouter.
+
+    The client is created lazily on first call and reused thereafter.
+    Raises ValueError if OPENROUTER_API_KEY is not set.
+    """
+    global _client
+    if _client is None:
+        api_key = os.getenv("OPENROUTER_API_KEY")
+        if not api_key:
+            raise ValueError("OPENROUTER_API_KEY environment variable not set")
+        _client = AsyncOpenAI(api_key=api_key, base_url=OPENROUTER_BASE_URL)
+    return _client
+
+
+def check_api_key() -> bool:
+    """Check whether the OpenRouter API key is present."""
+    return bool(os.getenv("OPENROUTER_API_KEY"))