feat(channel): KOOK 渠道适配器 + 框架兼容增强(wsutil/httpclient)

- plugins/channels/kook: config/adapter/gateway/websocket/send/message/errors — 实现 PlatformAdapter 13方法
  - WS 有状态网关: 取gateway地址→连WS→信令0/1/2/3/4/6 + 30s心跳/6s超时 + resume(拼接sn/session_id) + 指数退避重连
  - 收事件: 信令0 → UnifiedMessage(word注 channel_type/type/target_id/extra.author→字段)
  - 发消息: /message/create(频道) + /direct-message/create(私聊,修正正确端点,非user-chat) + Bearer鉴权
  - 注册 channels.go + CHANNELS_JSON 多账号 + channelbridge.configured 加 kook(bot_token非空才连)
- 框架增强: internal/channel/adapter/wsutil(连接管理/心跳/重连/resume骨架,复用gorilla,KOOK用上) + httpclient(Bearer+envelope归一,KOOK用)
- 全仓 go build/vet/test 绿, 零新依赖(复用餐gorilla), 未动telegram/qq/weixin/webhook契约
- §4.6 隔离/黑白名单/第三方边界未破坏

注: KOOK WS/WH 双模式待补(ReceiveMode), 实测需主人提供 CHANNEL_KOOK_TOKEN

internal/channel/adapter/wsutil/url.go

@@ -0,0 +1,85 @@
+package wsutil
+
+import (
+	"net/url"
+	"sort"
+	"strings"
+)
+
+// AppendQuery returns rawURL with the given query parameters added, preserving
+// any existing query string. Parameters with an empty value are omitted. It is
+// used by stateful gateway clients to splice resume parameters (resume/sn/
+// session_id) and access tokens onto a gateway URL before reconnecting. Keys are
+// appended in sorted order so the result is deterministic for tests.
+func AppendQuery(rawURL string, params map[string]string) string {
+	if len(params) == 0 {
+		return rawURL
+	}
+	u, err := url.Parse(rawURL)
+	if err != nil {
+		return appendNaive(rawURL, params)
+	}
+
+	keys := make([]string, 0, len(params))
+	for k := range params {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+
+	pairs := existingPairs(u.Query())
+	for _, k := range keys {
+		if params[k] == "" {
+			continue
+		}
+		pairs = append(pairs, url.QueryEscape(k)+"="+url.QueryEscape(params[k]))
+	}
+	u.RawQuery = strings.Join(pairs, "&")
+	return u.String()
+}
+
+// existingPairs flattens url.Values into ordered "k=v" pairs so that appending
+// new parameters produces a deterministic query string. Multi-valued keys keep
+// their original value order.
+func existingPairs(v url.Values) []string {
+	keys := make([]string, 0, len(v))
+	for k := range v {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	pairs := make([]string, 0, len(v))
+	for _, k := range keys {
+		for _, val := range v[k] {
+			pairs = append(pairs, url.QueryEscape(k)+"="+url.QueryEscape(val))
+		}
+	}
+	return pairs
+}
+
+// appendNaive appends query parameters to a URL that could not be parsed, using
+// '?' or '&' based on what is already present.
+func appendNaive(rawURL string, params map[string]string) string {
+	sep := "?"
+	if strings.Contains(rawURL, "?") {
+		sep = "&"
+	}
+	var b strings.Builder
+	b.WriteString(rawURL)
+	b.WriteString(sep)
+	keys := make([]string, 0, len(params))
+	for k := range params {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	first := true
+	for _, k := range keys {
+		if params[k] == "" {
+			continue
+		}
+		if !first {
+			b.WriteString("&")
+		}
+		first = false
+		b.WriteString(url.QueryEscape(k) + "=" + url.QueryEscape(params[k]))
+	}
+	return b.String()
+}