Add explicit encoding="utf-8" to all config/data file open() calls

On Windows, open() defaults to the system locale encoding (cp1252,
cp1254, etc.) rather than UTF-8. This breaks any file containing
non-ASCII characters, and also causes crashes when writing JSON with
ensure_ascii=False.

This adds encoding="utf-8" to open() calls in:
- gateway/run.py (config.yaml reads/writes throughout)
- gateway/config.py (gateway.json and config.yaml)
- hermes_cli/config.py (config.yaml load/save)
- hermes_cli/main.py (session export with ensure_ascii=False)
- hermes_cli/status.py (jobs.json and sessions.json)

hermes_cli/config.py

@@ -601,9 +601,9 @@ def load_config() -> Dict[str, Any]:
     
     if config_path.exists():
         try:
-            with open(config_path) as f:
+            with open(config_path, encoding="utf-8") as f:
                 user_config = yaml.safe_load(f) or {}
-            
+
             config = _deep_merge(config, user_config)
         except Exception as e:
             print(f"Warning: Failed to load config: {e}")
@@ -616,7 +616,7 @@ def save_config(config: Dict[str, Any]):
     ensure_hermes_home()
     config_path = get_config_path()
     
-    with open(config_path, 'w') as f:
+    with open(config_path, 'w', encoding="utf-8") as f:
         yaml.dump(config, f, default_flow_style=False, sort_keys=False)
 
 
@@ -840,7 +840,7 @@ def set_config_value(key: str, value: str):
     user_config = {}
     if config_path.exists():
         try:
-            with open(config_path) as f:
+            with open(config_path, encoding="utf-8") as f:
                 user_config = yaml.safe_load(f) or {}
         except Exception:
             user_config = {}
@@ -868,7 +868,7 @@ def set_config_value(key: str, value: str):
     
     # Write only user config back (not the full merged defaults)
     ensure_hermes_home()
-    with open(config_path, 'w') as f:
+    with open(config_path, 'w', encoding="utf-8") as f:
         yaml.dump(user_config, f, default_flow_style=False, sort_keys=False)
     
     # Keep .env in sync for keys that terminal_tool reads directly from env vars.