feat(weixin_ilink): 出站媒体走通（主人已批的三项）

按官方包 @tencent-weixin/openclaw-weixin 2.4.9 源码对齐：
① 上传由 PUT 改 POST；② 上传凭据读响应头 x-encrypted-param；
③ nativeMediaItem 改为官方 *_item.media.encrypt_query_param 嵌套形状（含 aes_key，
图片优先 image_item.aeskey）。
配合前一版已修的两点（入站按条密钥、媒体失败不阻断文本），机器人现在可主动发出文件/图片。
（逐项测试、变异红行与诚实边界见该切片报告）

plugins/channels/weixin_ilink/send_media_failure_test.go

@@ -23,15 +23,20 @@ import (
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/logger"
 )
 
-// mediaSendServer 是假 iLink：getuploadurl 按 upload 作答，上传成功，sendmessage 回 ret:0。
+// mediaSendServer 是假 iLink：getuploadurl 按 upload 作答，**CDN 上传按官方口径回
+// 200 + `x-encrypted-param` 头**（POST），sendmessage 回 ret:0。
 func mediaSendServer(t *testing.T, rec *reqRecorder, upload handlerResult) *httptest.Server {
 	t.Helper()
 	return newJSONServer(t, rec, func(req recordedReq) handlerResult {
 		switch {
 		case req.method == http.MethodPost && req.path == "/ilink/bot/getuploadurl":
 			return upload
-		case req.method == http.MethodPut:
-			return handlerResult{status: http.StatusOK, body: []byte("ok")}
+		case req.method == http.MethodPost && req.path == "/cdn/up":
+			return handlerResult{
+				status:  http.StatusOK,
+				body:    []byte("ok"),
+				headers: map[string]string{uploadParamHeader: downloadParamFixture},
+			}
 		case req.method == http.MethodPost && req.path == "/ilink/bot/sendmessage":
 			return handlerResult{body: jsonBody(map[string]any{"ret": 0})}
 		default:
@@ -40,6 +45,10 @@ func mediaSendServer(t *testing.T, rec *reqRecorder, upload handlerResult) *http
 	})
 }
 
+// downloadParamFixture 是假 CDN 回填的下载凭据（真实值由服务端生成，测试只关心它被
+// 原样带进 item 的 media.encrypt_query_param）。
+const downloadParamFixture = "dl+param/1="
+
 // newLoggingSendAdapter 装配一个把日志写进 buf 的已连接适配器，用来断言失败**不静默**。
 func newLoggingSendAdapter(t *testing.T, srv *httptest.Server, buf *bytes.Buffer) *Adapter {
 	t.Helper()
@@ -193,9 +202,9 @@ func TestGetUploadURL_RequestCarriesProtocolFields(t *testing.T) {
 	if err != nil {
 		t.Fatalf("aeskey 不是十六进制：%v", err)
 	}
-	puts := rec.find(func(q recordedReq) bool { return q.method == http.MethodPut })
-	if len(puts) != 0 {
-		t.Fatalf("上传地址缺失时不该发起上传：%d 次", len(puts))
+	// 上传地址缺失时**一次上传请求都不该发出**（只应有那一次 getuploadurl）。
+	if reqs := rec.find(func(q recordedReq) bool { return q.method == http.MethodPost }); len(reqs) != 1 {
+		t.Fatalf("POST 请求 = %d 次, want 1（只有 getuploadurl；地址缺失就不该上传）", len(reqs))
 	}
 	if len(rawKey) != 16 {
 		t.Fatalf("aeskey = %d 字节, want 16", len(rawKey))
@@ -212,8 +221,12 @@ func TestOutboundMedia_UsesUploadFullURL(t *testing.T) {
 		switch {
 		case req.method == http.MethodPost && req.path == "/ilink/bot/getuploadurl":
 			return handlerResult{body: jsonBody(map[string]any{"upload_full_url": srv.URL + "/cdn/up"})}
-		case req.method == http.MethodPut && req.path == "/cdn/up":
-			return handlerResult{status: http.StatusOK, body: []byte("ok")}
+		case req.method == http.MethodPost && req.path == "/cdn/up":
+			return handlerResult{
+				status:  http.StatusOK,
+				body:    []byte("ok"),
+				headers: map[string]string{uploadParamHeader: downloadParamFixture},
+			}
 		case req.method == http.MethodPost && req.path == "/ilink/bot/sendmessage":
 			return handlerResult{body: jsonBody(map[string]any{"ret": 0})}
 		default:
@@ -248,8 +261,12 @@ func TestOutboundMedia_BuildsUploadURLFromUploadParam(t *testing.T) {
 		switch {
 		case req.method == http.MethodPost && req.path == "/ilink/bot/getuploadurl":
 			return handlerResult{body: jsonBody(map[string]any{"upload_param": "ab+cd="})}
-		case req.method == http.MethodPut && req.path == "/upload":
-			return handlerResult{status: http.StatusOK, body: []byte("ok")}
+		case req.method == http.MethodPost && req.path == "/upload":
+			return handlerResult{
+				status:  http.StatusOK,
+				body:    []byte("ok"),
+				headers: map[string]string{uploadParamHeader: downloadParamFixture},
+			}
 		case req.method == http.MethodPost && req.path == "/ilink/bot/sendmessage":
 			return handlerResult{body: jsonBody(map[string]any{"ret": 0})}
 		default:
@@ -268,10 +285,13 @@ func TestOutboundMedia_BuildsUploadURLFromUploadParam(t *testing.T) {
 		t.Fatalf("SendMessage(media, upload_param): %v", err)
 	}
 
-	puts := rec.find(func(q recordedReq) bool { return q.method == http.MethodPut })
+	puts := rec.find(func(q recordedReq) bool { return q.path == "/upload" })
 	if len(puts) != 1 {
 		t.Fatalf("上传请求 = %d 次, want 1", len(puts))
 	}
+	if puts[0].method != http.MethodPost {
+		t.Fatalf("上传方法 = %s, want POST（官方口径）", puts[0].method)
+	}
 	if !strings.Contains(puts[0].query, "encrypted_query_param=ab%2Bcd%3D") {
 		t.Fatalf("上传查询串 = %q, want 转义后的 encrypted_query_param", puts[0].query)
 	}