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

plugins/channels/kook/config.go

@@ -0,0 +1,55 @@
+// Package kook implements the built-in KOOK (KaiHeiLa) channel adapter for
+// Cyrene v2. KOOK is a stateful WebSocket-gateway channel: inbound events are
+// delivered over a gateway WebSocket (hello/heartbeat/event/resume signaling),
+// while outbound messages are sent over a bearer-authenticated REST API.
+//
+// The adapter conforms to internal/channel/adapter.PlatformAdapter, translating
+// native KOOK events into the normalized adapter.UnifiedMessage model and
+// delivering replies via /api/v3/message/create (channels) and
+// /api/v3/direct-message/create (private chat). Identity is carried as channel
+// actor metadata (author id + nickname) only — owner/member resolution is the
+// channel layer's job, never a prompt-text heuristic.
+//
+// The design authority is DevDocs/design/08-渠道接入.md §4 (kook) and §7
+// (framework reusability). It depends on internal/channel/adapter (including the
+// shared wsutil and httpclient primitives), internal/logger, and the standard
+// library. The bot token is never logged.
+package kook
+
+import (
+	"strings"
+	"time"
+)
+
+// Defaults and knobs for the KOOK integration.
+const (
+	// defaultBaseURL is the KOOK REST API root.
+	defaultBaseURL = "https://www.kookapp.cn/api/v3"
+	// defaultHTTPTimeout bounds a single REST request.
+	defaultHTTPTimeout = 30 * time.Second
+	// gatewayPath is the gateway-address fetch endpoint relative to baseURL.
+	gatewayPath = "/gateway/index"
+	// maxMessageLen is KOOK's documented per-message content limit.
+	maxMessageLen = 8000
+	// heartbeatInterval is how often the client sends a ping (KOOK: 30s).
+	heartbeatInterval = 30 * time.Second
+	// helloTimeout bounds the wait for the handshake (hello/resume ack).
+	helloTimeout = 6 * time.Second
+)
+
+// Config holds the settings required to reach the KOOK API.
+type Config struct {
+	// BotToken is the secret bot token issued by the KOOK developer center. It is
+	// surfaced through Config() but never written to logs.
+	BotToken string `json:"bot_token"`
+	// BaseURL is the KOOK REST API root; empty uses the production default.
+	BaseURL string `json:"base_url"`
+}
+
+// Validate checks the configuration for values needed to connect.
+func (c Config) Validate() error {
+	if strings.TrimSpace(c.BotToken) == "" {
+		return ErrMissingToken
+	}
+	return nil
+}