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)

gateway/config.py

@@ -260,7 +260,7 @@ def load_gateway_config() -> GatewayConfig:
     gateway_config_path = Path.home() / ".hermes" / "gateway.json"
     if gateway_config_path.exists():
         try:
-            with open(gateway_config_path, "r") as f:
+            with open(gateway_config_path, "r", encoding="utf-8") as f:
                 data = json.load(f)
                 config = GatewayConfig.from_dict(data)
         except Exception as e:
@@ -273,7 +273,7 @@ def load_gateway_config() -> GatewayConfig:
         import yaml
         config_yaml_path = Path.home() / ".hermes" / "config.yaml"
         if config_yaml_path.exists():
-            with open(config_yaml_path) as f:
+            with open(config_yaml_path, encoding="utf-8") as f:
                 yaml_cfg = yaml.safe_load(f) or {}
             sr = yaml_cfg.get("session_reset")
             if sr and isinstance(sr, dict):
@@ -411,5 +411,5 @@ def save_gateway_config(config: GatewayConfig) -> None:
     gateway_config_path = Path.home() / ".hermes" / "gateway.json"
     gateway_config_path.parent.mkdir(parents=True, exist_ok=True)
     
-    with open(gateway_config_path, "w") as f:
+    with open(gateway_config_path, "w", encoding="utf-8") as f:
         json.dump(config.to_dict(), f, indent=2)