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)

agent/memory_manager.py

@@ -34,6 +34,7 @@ import re
 from typing import Any, Dict, List, Optional
 
 from agent.memory_provider import MemoryProvider
+from tools.registry import tool_error
 
 logger = logging.getLogger(__name__)
 
@@ -249,7 +250,7 @@ class MemoryManager:
         """
         provider = self._tool_to_provider.get(tool_name)
         if provider is None:
-            return json.dumps({"error": f"No memory provider handles tool '{tool_name}'"})
+            return tool_error(f"No memory provider handles tool '{tool_name}'")
         try:
             return provider.handle_tool_call(tool_name, args, **kwargs)
         except Exception as e:
@@ -257,7 +258,7 @@ class MemoryManager:
                 "Memory provider '%s' handle_tool_call(%s) failed: %s",
                 provider.name, tool_name, e,
             )
-            return json.dumps({"error": f"Memory tool '{tool_name}' failed: {e}"})
+            return tool_error(f"Memory tool '{tool_name}' failed: {e}")
 
     # -- Lifecycle hooks -----------------------------------------------------