fix(kook): KOOK 机器人鉴权用 Authorization: Bot <token> 而非 Bearer

httpclient 硬编码 Bearer，导致 KOOK bot token 被当 OAuth2 用户令牌发，
/ gateway/index 返回 401『登录环境异常』。按 KOOK reference 鉴权规范，
给共享 httpclient 增加可配置 authScheme（默认 Bearer），KOOK 用 Bot。

- httpclient: 新增 WithAuthScheme 选项 + authScheme 字段，do() 按 scheme 组装
- kook/adapter: 装配时传 WithAuthScheme("Bot")
- 同步修正 config.go 注释与 send/identity 测试断言

plugins/channels/kook/adapter.go

@@ -105,9 +105,13 @@ func New(cfg Config, opts ...Option) *Adapter {
 			a.baseURL = defaultBaseURL
 		}
 	}
+	// KOOK authenticates bots with `Authorization: Bot <token>` (not "Bearer",
+	// which is reserved for OAuth2 user tokens). This is mandated by the KOOK
+	// reference: /doc/reference §鉴权.
 	a.http = httpclient.New(
 		httpclient.WithBaseURL(a.baseURL),
 		httpclient.WithToken(cfg.BotToken),
+		httpclient.WithAuthScheme("Bot"),
 		httpclient.WithHTTPClient(a.client),
 		httpclient.WithLogger(a.log),
 	)

plugins/channels/kook/config.go

@@ -3,7 +3,7 @@
 // modes: a WebSocket-gateway mode (events over a gateway WebSocket with
 // hello/heartbeat/event/resume signaling) and a Webhook mode (KOOK POSTs event
 // callbacks to a Cyrene gateway route). Outbound messages are always sent over a
-// bearer-authenticated REST API.
+// bot-token-authenticated REST API (`Authorization: Bot <token>`).
 //
 // The adapter conforms to internal/channel/adapter.PlatformAdapter, translating
 // native KOOK events into the normalized adapter.UnifiedMessage model and

plugins/channels/kook/identity_test.go

@@ -15,8 +15,8 @@ func TestFetchBotIdentity(t *testing.T) {
 			http.NotFound(w, r)
 			return
 		}
-		if got := r.Header.Get("Authorization"); got != "Bearer testtoken" {
-			t.Errorf("Authorization = %q, want Bearer testtoken", got)
+		if got := r.Header.Get("Authorization"); got != "Bot testtoken" {
+			t.Errorf("Authorization = %q, want Bot testtoken", got)
 		}
 		kookOK(w, map[string]any{"id": "bot-1", "username": "bot", "nickname": "小K"})
 	}))

plugins/channels/kook/send_test.go

@@ -38,8 +38,8 @@ func TestSendMessage_GroupText(t *testing.T) {
 	}
 	mu.Lock()
 	defer mu.Unlock()
-	if auth != "Bearer testtoken" {
-		t.Errorf("Authorization = %q, want Bearer testtoken", auth)
+	if auth != "Bot testtoken" {
+		t.Errorf("Authorization = %q, want Bot testtoken", auth)
 	}
 	if body["target_id"] != "chan-1" {
 		t.Errorf("target_id = %v, want chan-1", body["target_id"])