feat(client): HttpTransport — real HTTPRequest transport (untested shim)

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

client/scripts/net/http_transport.gd

@@ -0,0 +1,35 @@
+extends "res://scripts/net/dm_transport.gd"
+## The real transport: wraps an HTTPRequest Node the owner added to the tree.
+## This is the one untested shim in the slice — it needs a live Node and a
+## server, so it is verified by reading and by the harness live smoke, the same
+## way the server's HTTP boundary is covered only by its gated --run-live test.
+## A non-2xx status is NOT an error here; it is a normal DmResponse the service
+## interprets. Only a transport-level failure (no response) yields failed().
+
+const ProxyConfig = preload("res://scripts/net/proxy_config.gd")
+const DmResponse = preload("res://scripts/net/dm_response.gd")
+
+var _http: HTTPRequest
+
+
+func _init(http: HTTPRequest) -> void:
+	_http = http
+
+
+func post_json(path: String, body: Dictionary) -> DmResponse:
+	var url := ProxyConfig.base_url() + path
+	var headers := ["Content-Type: application/json"]
+	var payload := JSON.stringify(body)
+	var err := _http.request(url, headers, HTTPClient.METHOD_POST, payload)
+	if err != OK:
+		return DmResponse.failed("request() failed to start: error %d" % err)
+	# request_completed(result, response_code, headers, body) — awaiting a
+	# multi-arg signal returns the args as an Array.
+	var signal_args: Array = await _http.request_completed
+	var result: int = signal_args[0]
+	var response_code: int = signal_args[1]
+	var raw: PackedByteArray = signal_args[3]
+	if result != HTTPRequest.RESULT_SUCCESS:
+		return DmResponse.failed("transport result %d" % result)
+	var parsed = JSON.parse_string(raw.get_string_from_utf8())  # null if not JSON
+	return DmResponse.ok(response_code, parsed)

client/scripts/net/http_transport.gd.uid

@@ -0,0 +1 @@
+uid://cuvhnqsgr3liq