fix: normalize numeric MCP server names to str (fixes #6901)

YAML parses bare numeric keys (e.g. `12306:`) as int, causing
TypeError when sorted() is called on mixed int/str collections.

Changes:
- Normalize toolset_names entries to str in _get_platform_tools()
- Cast MCP server name to str(name) when building enabled_mcp_servers
- Add regression test

hermes_cli/tools_config.py

@@ -509,6 +509,10 @@ def _get_platform_tools(
         default_ts = PLATFORMS[platform]["default_toolset"]
         toolset_names = [default_ts]
 
+    # YAML may parse bare numeric names (e.g. ``12306:``) as int.
+    # Normalise to str so downstream sorted() never mixes types.
+    toolset_names = [str(ts) for ts in toolset_names]
+
     configurable_keys = {ts_key for ts_key, _, _ in CONFIGURABLE_TOOLSETS}
 
     # If the saved list contains any configurable keys directly, the user
@@ -567,7 +571,7 @@ def _get_platform_tools(
     # Special sentinel: "no_mcp" in the toolset list disables all MCP servers.
     mcp_servers = config.get("mcp_servers") or {}
     enabled_mcp_servers = {
-        name
+        str(name)
         for name, server_cfg in mcp_servers.items()
         if isinstance(server_cfg, dict)
         and _parse_enabled_flag(server_cfg.get("enabled", True), default=True)