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/agents/agent-editor.spec.ts

@@ -0,0 +1,25 @@
+import { test, expect, scenarioMarker, unique, AI_REPLY } from '@e2e'
+
+test.describe('agent editor', () => {
+  test('an agent created and edited in the dashboard answers with its new instructions @agents', async ({ makeAgent, agentsPage, makeWidget, llm }) => {
+    // With at least one agent, /ai-agents shows the list rather than onboarding.
+    await makeAgent()
+    const scenarioId = unique('scn')
+    const name = `UI Agent ${scenarioId}`
+
+    await agentsPage.goto()
+    const agentId = await agentsPage.createAgent(name)
+    await agentsPage.openAgent(agentId)
+    await agentsPage.setInstructions(`Always sign off as the Acme team. ${scenarioMarker(scenarioId)}`)
+
+    await llm.script({ name, scenarioId }, (s) => s.otherwise().reply('Hello from the Acme team!'))
+    const widget = await makeWidget(agentId)
+    await widget.embed()
+    await widget.open()
+    await widget.send('Hi there')
+
+    await expect(widget.lastAgentMessage()).toHaveText('Hello from the Acme team!', AI_REPLY)
+    const prompts = (await llm.requests({ name, scenarioId })).map((request) => request.system)
+    expect(prompts.join('\n')).toContain('Always sign off as the Acme team.')
+  })
+})