refactor: add tool_error/tool_result helpers + read_raw_config, migrate 129 callsites

Add three reusable helpers to eliminate pervasive boilerplate:

tools/registry.py — tool_error() and tool_result():
  Every tool handler returns JSON strings. The pattern
  json.dumps({"error": msg}, ensure_ascii=False) appeared 106 times,
  and json.dumps({"success": False, "error": msg}, ...) another 23.
  Now: tool_error(msg) or tool_error(msg, success=False).

  tool_result() handles arbitrary result dicts:
  tool_result(success=True, data=payload) or tool_result(some_dict).

hermes_cli/config.py — read_raw_config():
  Lightweight YAML reader that returns the raw config dict without
  load_config()'s deep-merge + migration overhead. Available for
  callsites that just need a single config value.

Migration (129 callsites across 32 files):
- tools/: browser_camofox (18), file_tools (10), homeassistant (8),
  web_tools (7), skill_manager (7), cronjob (11), code_execution (4),
  delegate (5), send_message (4), tts (4), memory (7), session_search (3),
  mcp (2), clarify (2), skills_tool (3), todo (1), vision (1),
  browser (1), process_registry (2), image_gen (1)
- plugins/memory/: honcho (9), supermemory (9), hindsight (8),
  holographic (7), openviking (7), mem0 (7), byterover (6), retaindb (2)
- agent/: memory_manager (2), builtin_memory_provider (1)

plugins/memory/mem0/__init__.py

@@ -23,6 +23,7 @@ import time
 from typing import Any, Dict, List
 
 from agent.memory_provider import MemoryProvider
+from tools.registry import tool_error
 
 logger = logging.getLogger(__name__)
 
@@ -305,7 +306,7 @@ class Mem0MemoryProvider(MemoryProvider):
         try:
             client = self._get_client()
         except Exception as e:
-            return json.dumps({"error": str(e)})
+            return tool_error(str(e))
 
         if tool_name == "mem0_profile":
             try:
@@ -317,12 +318,12 @@ class Mem0MemoryProvider(MemoryProvider):
                 return json.dumps({"result": "\n".join(lines), "count": len(lines)})
             except Exception as e:
                 self._record_failure()
-                return json.dumps({"error": f"Failed to fetch profile: {e}"})
+                return tool_error(f"Failed to fetch profile: {e}")
 
         elif tool_name == "mem0_search":
             query = args.get("query", "")
             if not query:
-                return json.dumps({"error": "Missing required parameter: query"})
+                return tool_error("Missing required parameter: query")
             rerank = args.get("rerank", False)
             top_k = min(int(args.get("top_k", 10)), 50)
             try:
@@ -339,12 +340,12 @@ class Mem0MemoryProvider(MemoryProvider):
                 return json.dumps({"results": items, "count": len(items)})
             except Exception as e:
                 self._record_failure()
-                return json.dumps({"error": f"Search failed: {e}"})
+                return tool_error(f"Search failed: {e}")
 
         elif tool_name == "mem0_conclude":
             conclusion = args.get("conclusion", "")
             if not conclusion:
-                return json.dumps({"error": "Missing required parameter: conclusion"})
+                return tool_error("Missing required parameter: conclusion")
             try:
                 client.add(
                     [{"role": "user", "content": conclusion}],
@@ -355,9 +356,9 @@ class Mem0MemoryProvider(MemoryProvider):
                 return json.dumps({"result": "Fact stored."})
             except Exception as e:
                 self._record_failure()
-                return json.dumps({"error": f"Failed to store: {e}"})
+                return tool_error(f"Failed to store: {e}")
 
-        return json.dumps({"error": f"Unknown tool: {tool_name}"})
+        return tool_error(f"Unknown tool: {tool_name}")
 
     def shutdown(self) -> None:
         for t in (self._prefetch_thread, self._sync_thread):