feat(contract,gateway): B4 枚举权威表 — GET /api/v1/meta/enums + 未知值回落约定

- 新增 internal/contract/enums 叶子包：platform/mood/mode 三表 + UnknownFallback="display-raw"；每次调用返回新切片，无包级可变全局
- GET /api/v1/meta/enums（anyAuth 只读、纯投影、无 store/无错误路径）
- 反漂移 4 处：真构造内置适配器断言 Name() 与表双向相等、真工厂 buildAccountAdapter 逐项可建、mood 对齐 emotion 常量 + 默认转移表、mode 对齐前端 MODES（跨语言，文件缺失则 skip）
- Docs/api-client §1.1 枚举权威表 + 行15 + v0.38；api-reference §3.7 + 行12

cmd/cyrene/enums_factory_test.go

@@ -0,0 +1,46 @@
+package main
+
+// Wiring-level anti-drift test for the shared client enum table (design/07 §6).
+// The enums package test pins the platform table to the adapters' Name() values;
+// this one pins it to the composition root's factory — every platform the table
+// publishes must be one buildAccountAdapter actually knows how to build, so a
+// phantom entry (a platform listed for clients but never wired up) fails here.
+
+import (
+	"io"
+	"testing"
+
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/config"
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/contract/enums"
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/logger"
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/history"
+)
+
+// TestChannelFactoryBuildsEnumeratedPlatforms builds every adapter the published
+// platform table lists (other than the Web main-session source, which is not an
+// adapter) through the real factory and asserts the built adapter's Name()
+// resolves back to that platform. Adapter construction never dials out, so the
+// minimal configs below are enough.
+func TestChannelFactoryBuildsEnumeratedPlatforms(t *testing.T) {
+	t.Parallel()
+	log := logger.New(logger.Options{Out: io.Discard})
+	minimalConfig := map[string]map[string]any{
+		"kook":     {"bot_token": "test"},
+		"telegram": {"bot_token": "test"},
+	}
+
+	for _, p := range enums.Platforms() {
+		if p.ID == history.PlatformWeb {
+			continue
+		}
+		acct := config.ChannelAccount{Config: minimalConfig[p.ID]}
+		built, err := buildAccountAdapter(p.ID, acct, log)
+		if err != nil {
+			t.Errorf("platform %q is published to clients but the factory cannot build it: %v", p.ID, err)
+			continue
+		}
+		if got := barePlatform(built.Name()); got != p.ID {
+			t.Errorf("buildAccountAdapter(%q).Name() = %q, want %q", p.ID, got, p.ID)
+		}
+	}
+}