feat(channel): 消息契约加「她自己账号 id / 是否在叫她」结构化判据并接线 qq_obv11

契约（internal/channel/adapter）：UnifiedMessage 新增三个字段 —— SelfID（她自己在该
平台的账号 id）、MentionAll（是否 @全体，design/26 §2.4 的 mention_all）、AddressedToMe
（本条是否指向她本人）；判据的唯一出处是新增的 MentionedSelf（结构化 id 精确比对，
空 selfID 一律 false）与 AddressedToSelf（私聊恒 true；群聊 = 点名她或 @全体；
平台未给 SelfID ⇒ fail-closed）。全程不匹配正文文本。

接线（plugins/channels/qq_obv11）：新增 addressed.go，把事件里早已解出、此前只用于
debug 日志与 notice 判定的 self_id 接进 toUnified，并从 at 段解出 @全体（qq=all），
在 ChannelType 判定之后统一回写三个字段。

design/18 §2 触发① 的旧口径「Mentions 非空」= @谁不论（实测群 672432767 里 @别人两次
被回）；本片让消费侧（light.go:142，归 M12）能改用 AddressedToMe || MentionAll。
既有字段 Mentions/ReplyToID/ReplyToText 语义与形状不变。

测试：qq_obv11 十种帧形态（私聊/@她/@别人/@全体/无@/CQ 形态/fail-closed/纯回复）
逐条断言；adapter 侧覆盖 MentionedSelf 与 AddressedToSelf。变异自证：判据改回
「Mentions 非空」⇒ group_mention_other 红；摘掉 selfId 接线 ⇒ group_mention_me 红。

internal/channel/adapter/message_test.go

@@ -149,3 +149,105 @@ func TestContentTypeValid(t *testing.T) {
 		t.Error("bogus ContentType.Valid() = true, want false")
 	}
 }
+
+func TestMentionedSelf(t *testing.T) {
+	t.Parallel()
+
+	mentions := []Mention{{UserID: "all"}, {UserID: "u-2"}}
+
+	tests := []struct {
+		name     string
+		selfID   string
+		mentions []Mention
+		want     bool
+	}{
+		{name: "platform has not provided self id", selfID: "", mentions: mentions, want: false},
+		{name: "no mentions", selfID: "u-2", mentions: nil, want: false},
+		{name: "points at someone else", selfID: "u-9", mentions: mentions, want: false},
+		{name: "points at her", selfID: "u-2", mentions: mentions, want: true},
+		{name: "at-all marker is not a user id", selfID: "all", mentions: nil, want: false},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			if got := MentionedSelf(tt.selfID, tt.mentions); got != tt.want {
+				t.Errorf("MentionedSelf(%q, %+v) = %v, want %v", tt.selfID, tt.mentions, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestAddressedToSelf(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name string
+		msg  UnifiedMessage
+		want bool
+	}{
+		{
+			name: "private chat is always addressed to her",
+			msg:  UnifiedMessage{ChannelType: ChannelDirect, SelfID: "u-1"},
+			want: true,
+		},
+		{
+			name: "private chat without platform self id stays addressed",
+			msg:  UnifiedMessage{ChannelType: ChannelDirect},
+			want: true,
+		},
+		{
+			name: "group mentions her",
+			msg: UnifiedMessage{
+				ChannelType: ChannelGroup, GroupID: "g-1", SelfID: "u-1",
+				Mentions: []Mention{{UserID: "u-1"}},
+			},
+			want: true,
+		},
+		{
+			name: "group mentions someone else",
+			msg: UnifiedMessage{
+				ChannelType: ChannelGroup, GroupID: "g-1", SelfID: "u-1",
+				Mentions: []Mention{{UserID: "u-2"}},
+			},
+			want: false,
+		},
+		{
+			name: "group mentions all",
+			msg: UnifiedMessage{
+				ChannelType: ChannelGroup, GroupID: "g-1", SelfID: "u-1", MentionAll: true,
+				Mentions: []Mention{{UserID: "all"}},
+			},
+			want: true,
+		},
+		{
+			name: "group without mention",
+			msg:  UnifiedMessage{ChannelType: ChannelGroup, GroupID: "g-1", SelfID: "u-1"},
+			want: false,
+		},
+		{
+			name: "group without platform self id is fail-closed",
+			msg: UnifiedMessage{
+				ChannelType: ChannelGroup, GroupID: "g-1",
+				Mentions: []Mention{{UserID: "u-1"}},
+			},
+			want: false,
+		},
+		{
+			name: "zero value stays fail-closed for adapters that do not wire it",
+			msg:  UnifiedMessage{},
+			want: false,
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			if got := tt.msg.AddressedToSelf(); got != tt.want {
+				t.Errorf("AddressedToSelf() = %v, want %v (msg=%+v)", got, tt.want, tt.msg)
+			}
+		})
+	}
+}