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

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

client/scripts/net/dm_response.gd

@@ -0,0 +1,25 @@
+class_name DmResponse
+extends RefCounted
+## The raw outcome of one HTTP attempt, independent of any game meaning.
+## `status` is 0 when the transport never reached the server; `body` is the
+## parsed JSON dict, or null when the body was absent or not JSON.
+
+var status: int
+var body                      # Variant: parsed JSON (Dictionary) or null
+var transport_ok: bool
+var error: String
+
+
+func _init(p_status := 0, p_body = null, p_transport_ok := false, p_error := "") -> void:
+	status = p_status
+	body = p_body
+	transport_ok = p_transport_ok
+	error = p_error
+
+
+static func ok(p_status: int, p_body) -> DmResponse:
+	return DmResponse.new(p_status, p_body, true, "")
+
+
+static func failed(p_error: String) -> DmResponse:
+	return DmResponse.new(0, null, false, p_error)