feat(embed,ui04): E01 v2 contract skeleton — displayMode/scrollSpeed/reactionsEnabled, v2 loader entry and fixed 195x280 shell

- contracts: EmbedSlotSettings optional v2 fields (carousel default) + SlotSettingsPayload; gen + redocly green
- api: DTO validation + normalization full-set (cn manage + ov public projection share normalizeStoredSettings)
- embed-loader: params v2 parse/merge/url family, loader-v2.js fixed shell (border/radius/#10161E/safe-area, resize ignored, stack gap 12), dual-artifact build+sync; v1 source frozen
- viewer: EmbedPage v=2 branch, EmbedStream (viewport/track/real anchors/collapse/empty), stream.ts pure fns, i18n zh/en
- admin: types + utils (create default vertical-stream, clampScrollSpeed, v1/v2 snippet selection)
- tests: loader 36 (+9 v2), viewer 222, admin 82, api unit 51, v1 embed e2e 20, v2 E01 gate 2 (195x280 desktop+mobile cross-origin, no footer)

Co-Authored-By: Claude Code <noreply@anthropic.com>

packages/contracts/src/events.ts

@@ -157,6 +157,9 @@ export interface SlotSettingsPayload {
   offsetX?: number; // 0..120（默认 16）
   offsetBottom?: number; // 0..240（默认 24）
   zIndex?: number; // 1..2147483000（默认 1000）
+  displayMode?: string; // carousel|vertical-stream（默认 carousel，UI-04）
+  scrollSpeed?: number; // 8..32 CSS px/s（默认 16，UI-04；仅 v2 生效）
+  reactionsEnabled?: boolean; // 默认 true（UI-04；false 仅隐藏气泡）
 }
 
 // 运行时校验用：全部合法事件类型字符串。satisfies 保证 数组 ⊆ 接口 union；