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)

tools/skills_tool.py

@@ -76,7 +76,7 @@ from enum import Enum
 from pathlib import Path
 from typing import Dict, Any, List, Optional, Set, Tuple
 
-from tools.registry import registry
+from tools.registry import registry, tool_error
 
 logger = logging.getLogger(__name__)
 
@@ -713,7 +713,7 @@ def skills_categories(verbose: bool = False, task_id: str = None) -> str:
         )
 
     except Exception as e:
-        return json.dumps({"success": False, "error": str(e)}, ensure_ascii=False)
+        return tool_error(str(e), success=False)
 
 
 def skills_list(category: str = None, task_id: str = None) -> str:
@@ -781,7 +781,7 @@ def skills_list(category: str = None, task_id: str = None) -> str:
         )
 
     except Exception as e:
-        return json.dumps({"success": False, "error": str(e)}, ensure_ascii=False)
+        return tool_error(str(e), success=False)
 
 
 def skill_view(name: str, file_path: str = None, task_id: str = None) -> str:
@@ -1255,7 +1255,7 @@ def skill_view(name: str, file_path: str = None, task_id: str = None) -> str:
         return json.dumps(result, ensure_ascii=False)
 
     except Exception as e:
-        return json.dumps({"success": False, "error": str(e)}, ensure_ascii=False)
+        return tool_error(str(e), success=False)
 
 
 # Tool description for model_tools.py