feat(client): net primitives — DmResponse, NarrateResult, DmTransport, ProxyConfig

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

client/scripts/net/proxy_config.gd

@@ -0,0 +1,14 @@
+class_name ProxyConfig
+extends RefCounted
+## The client's one piece of network config: the proxy base URL. Never a key,
+## never a model name (charter §4). Overridable per environment via project
+## settings; defaults to the dev proxy.
+
+const SETTING := "coc_rpg/proxy_base_url"
+const DEFAULT := "http://localhost:8000"
+
+
+static func base_url() -> String:
+	var v = ProjectSettings.get_setting(SETTING, DEFAULT)
+	var s := str(v)
+	return s if s != "" else DEFAULT