feat(contracts): UniversalRow 契约 v1 冻结 + 守卫 + 测试

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

packages/contracts/src/index.ts

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+export * from './universal-row.js'

packages/contracts/src/universal-row.ts

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+export const UNIVERSAL_ROW_VERSION = 1
+
+export interface UniversalRow {
+  sourceType: string
+  sourceId: string
+  status: string
+  locale: string
+  sourceUrl?: string
+  slug?: string
+  title?: string
+  excerpt?: string
+  bodyHtml?: string
+  publishedAt?: string
+  modifiedAt?: string
+  taxonomyRefs: Array<{ taxonomy: string; sourceTermId: string }>
+  attachmentRefs: Array<{ role: string; sourceId?: string; sourceUrl?: string }>
+  seo: Record<string, unknown>
+  knownFields: Record<string, unknown>
+  extras: Record<string, unknown>
+  rawLocation: string
+}
+
+const REQUIRED: (keyof UniversalRow)[] = [
+  'sourceType', 'sourceId', 'status', 'locale',
+  'taxonomyRefs', 'attachmentRefs', 'seo', 'knownFields', 'extras', 'rawLocation',
+]
+
+export function isUniversalRow(v: unknown): v is UniversalRow {
+  if (typeof v !== 'object' || v === null) return false
+  const row = v as Record<string, unknown>
+  return REQUIRED.every((k) => k in row)
+    && Array.isArray(row.taxonomyRefs) && Array.isArray(row.attachmentRefs)
+    && row.seo !== null && typeof row.seo === 'object'
+    && row.knownFields !== null && typeof row.knownFields === 'object'
+    && row.extras !== null && typeof row.extras === 'object'
+}