docs: 交付文档、维护指引与端到端回归

补齐 README、开发计划、维护交接与 E2E 用例，执行最终验收。

e2e/specs/knowledge/knowledge-answer.spec.ts

@@ -0,0 +1,27 @@
+import { test, expect, addKnowledgeText, unique, AI_REPLY } from '@e2e'
+
+test.describe('knowledge base', () => {
+  test('an answer is grounded in text added to the knowledge base @smoke @knowledge', async ({ agent, widget, llm, adminApi, org }) => {
+    // A token no model could guess, so finding it in the search result proves the
+    // text was indexed and retrieved — not echoed from the prompt.
+    const policyCode = unique('RET')
+    await addKnowledgeText(adminApi, {
+      orgId: org.orgId,
+      agentId: agent.id,
+      title: `Returns policy ${policyCode}`, // titles are unique per org
+      content: `Returns policy: items can be returned within 45 days of delivery. Quote reference ${policyCode} on the return label.`,
+    })
+    await llm.script(agent, (s) => s
+      .when(/return/i).callTool('search_knowledge_base', { query: 'returns policy' })
+      .thenReply('You can return items within 45 days of delivery.')
+      .otherwise().reply('Happy to help!'))
+
+    await widget.embed()
+    await widget.open()
+    await widget.send('What is your returns policy?')
+
+    await expect(widget.lastAgentMessage()).toHaveText('You can return items within 45 days of delivery.', AI_REPLY)
+    const searchResults = (await llm.requests(agent)).flatMap((request) => request.toolResults)
+    expect(searchResults.join('\n')).toContain(policyCode)
+  })
+})