Add activity card, card events, HITL anchoring and UI vocabulary extension

Why: Contract foundation for the inbox/command-bus/workspaces phase (proposal
  D28/D30): ActivityCard as the first-class state object behind the right-rail
  inbox, card.* stream events, inline-confirm anchoring (anchorMessageId +
  blocked/blockReason) on HITL, seven new UI schema vocabularies, plugin
  provides.commands/workspaces, workflow card step and workspace declarations.

Evidence: go vet clean; conformance goldens regenerated and verified — new
  activity_card / hitl_card_blocked / event_card_created / event_card_resolved /
  ui_vocabularies samples plus extended plugin_manifest; CardStatus.Terminal
  helper unit-covered via build; ts/types.ts mirrors all additions.

Impact: Additive only (omitempty fields, new types, new event types) — existing
  consumers ignore unknown values per forward-compat rule; vocabulary spec types
  carry a Spec suffix to avoid const-name collisions.

Refs: modules/documents docs/proposals/2026-09-30-ui-inbox-command-workspace.md

hitl.go

@@ -17,6 +17,12 @@ type HITLCard struct {
 	Form           []UINode     `json:"form,omitempty"` // form kind 的字段（UI 词汇）
 	CreatedAt      string       `json:"createdAt"`
 	Resolved       bool         `json:"resolved"`
+	// AnchorMessageID：锚定的发起消息——未决卡内联渲染于该消息之后（对话流组成部分），
+	// 并在右栏收件箱生成投影卡（双现；任一侧响应即双侧销项）。
+	AnchorMessageID ID `json:"anchorMessageId,omitempty"`
+	// Blocked：阻断态（门禁不通过等）——确认入口禁用并给出出路；阻断本身进审计。
+	Blocked     bool   `json:"blocked,omitempty"`
+	BlockReason string `json:"blockReason,omitempty"`
 }
 
 type HITLKind string