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/retaindb/__init__.py

@@ -34,6 +34,7 @@ from typing import Any, Dict, List
 from urllib.parse import quote
 
 from agent.memory_provider import MemoryProvider
+from tools.registry import tool_error
 
 logger = logging.getLogger(__name__)
 
@@ -649,11 +650,11 @@ class RetainDBMemoryProvider(MemoryProvider):
 
     def handle_tool_call(self, tool_name: str, args: dict, **kwargs) -> str:
         if not self._client:
-            return json.dumps({"error": "RetainDB not initialized"})
+            return tool_error("RetainDB not initialized")
         try:
             return json.dumps(self._dispatch(tool_name, args))
         except Exception as exc:
-            return json.dumps({"error": str(exc)})
+            return tool_error(str(exc))
 
     def _dispatch(self, tool_name: str, args: dict) -> Any:
         c = self._client