fix: thread safety for concurrent subagent delegation (#1672)

* fix: thread safety for concurrent subagent delegation

Four thread-safety fixes that prevent crashes and data races when
running multiple subagents concurrently via delegate_task:

1. Remove redirect_stdout/stderr from delegate_tool — mutating global
   sys.stdout races with the spinner thread when multiple children start
   concurrently, causing segfaults. Children already run with
   quiet_mode=True so the redirect was redundant.

2. Split _run_single_child into _build_child_agent (main thread) +
   _run_single_child (worker thread). AIAgent construction creates
   httpx/SSL clients which are not thread-safe to initialize
   concurrently.

3. Add threading.Lock to SessionDB — subagents share the parent's
   SessionDB and call create_session/append_message from worker threads
   with no synchronization.

4. Add _active_children_lock to AIAgent — interrupt() iterates
   _active_children while worker threads append/remove children.

5. Add _client_cache_lock to auxiliary_client — multiple subagent
   threads may resolve clients concurrently via call_llm().

Based on PR #1471 by peteromallet.

* feat: Honcho base_url override via config.yaml + quick command alias type

Two features salvaged from PR #1576:

1. Honcho base_url override: allows pointing Hermes at a remote
   self-hosted Honcho deployment via config.yaml:

     honcho:
       base_url: "http://192.168.x.x:8000"

   When set, this overrides the Honcho SDK's environment mapping
   (production/local), enabling LAN/VPN Honcho deployments without
   requiring the server to live on localhost. Uses config.yaml instead
   of env var (HONCHO_URL) per project convention.

2. Quick command alias type: adds a new 'alias' quick command type
   that rewrites to another slash command before normal dispatch:

     quick_commands:
       sc:
         type: alias
         target: /context

   Supports both CLI and gateway. Arguments are forwarded to the
   target command.

Based on PR #1576 by redhelix.

---------

Co-authored-by: peteromallet <peteromallet@users.noreply.github.com>
Co-authored-by: redhelix <redhelix@users.noreply.github.com>

agent/auxiliary_client.py

@@ -39,6 +39,7 @@ custom OpenAI-compatible endpoint without touching the main model settings.
 import json
 import logging
 import os
+import threading
 from pathlib import Path
 from types import SimpleNamespace
 from typing import Any, Dict, List, Optional, Tuple
@@ -1171,6 +1172,7 @@ def auxiliary_max_tokens_param(value: int) -> dict:
 
 # Client cache: (provider, async_mode, base_url, api_key) -> (client, default_model)
 _client_cache: Dict[tuple, tuple] = {}
+_client_cache_lock = threading.Lock()
 
 
 def _get_cached_client(
@@ -1182,9 +1184,11 @@ def _get_cached_client(
 ) -> Tuple[Optional[Any], Optional[str]]:
     """Get or create a cached client for the given provider."""
     cache_key = (provider, async_mode, base_url or "", api_key or "")
-    if cache_key in _client_cache:
-        cached_client, cached_default = _client_cache[cache_key]
-        return cached_client, model or cached_default
+    with _client_cache_lock:
+        if cache_key in _client_cache:
+            cached_client, cached_default = _client_cache[cache_key]
+            return cached_client, model or cached_default
+    # Build outside the lock
     client, default_model = resolve_provider_client(
         provider,
         model,
@@ -1193,7 +1197,11 @@ def _get_cached_client(
         explicit_api_key=api_key,
     )
     if client is not None:
-        _client_cache[cache_key] = (client, default_model)
+        with _client_cache_lock:
+            if cache_key not in _client_cache:
+                _client_cache[cache_key] = (client, default_model)
+            else:
+                client, default_model = _client_cache[cache_key]
     return client, model or default_model