feat: 提示词链显示层级走势、每轮改了多少行；课堂总结加“怎么问的 AI”

- 提示词弹框：顶部每轮一根层级柱子，点了跳到那一轮；每轮标出代码比上一版 +/− 多少行
  （没改标“代码没变”），和前面某轮一字不差的提问标“重复提问”
- 课堂总结：每人最新一版平均几轮、一轮就交、最后一版用外部 AI、问过引导的比例，
  以及各层级提问次数
- prompt_message 加两个覆盖索引，统计只读小列（像素画板全部班级 197 份约 0.3 ms）

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/src/db.ts

@@ -47,6 +47,9 @@ CREATE INDEX IF NOT EXISTS "prompt_conversation_user_id_ecc418b3" ON "prompt_con
 CREATE TABLE IF NOT EXISTS "prompt_message" ("id" integer NOT NULL PRIMARY KEY AUTOINCREMENT, "role" varchar(10) NOT NULL, "content" text NOT NULL, "code_html" text NULL, "code_css" text NULL, "code_js" text NULL, "created" datetime NOT NULL, "conversation_id" char(32) NOT NULL REFERENCES "prompt_conversation" ("id") DEFERRABLE INITIALLY DEFERRED, "prompt_level" integer NULL, "source" varchar(12) NOT NULL, "submission_id" char(32) NULL UNIQUE REFERENCES "submission_submission" ("id") DEFERRABLE INITIALLY DEFERRED);
 CREATE INDEX IF NOT EXISTS "prompt_message_conversation_id_af18dd4b" ON "prompt_message" ("conversation_id");
 CREATE INDEX IF NOT EXISTS "prompt_message_prompt_level_e461b596" ON "prompt_message" ("prompt_level");
+-- 课堂总结统计提示词链用的覆盖索引：只读小列，不碰 content / code_*
+CREATE INDEX IF NOT EXISTS "prompt_message_chain" ON "prompt_message" ("conversation_id", "created", "id", "role", "source", "prompt_level");
+CREATE INDEX IF NOT EXISTS "prompt_message_submission" ON "prompt_message" ("submission_id", "conversation_id", "created", "source") WHERE "submission_id" IS NOT NULL;
 
 -- 登录用 JWT：access token 不落库，refresh token 只存 sha256
 DROP TABLE IF EXISTS "auth_session";

server/src/routes/submission.ts

@@ -26,6 +26,7 @@ import {
   getActiveConversation,
   getPrecedingUserMessage,
   insertMessage,
+  promptChainStats,
   type MessageRow,
 } from "../services/prompt"
 import { pyRound } from "../services/pyround"
@@ -473,6 +474,8 @@ router.get("/stats/:task_id", (c) => {
     present_count: studentSubs.filter((s) => s.flag === "present").length,
     classes,
     top_scored: topScored,
+    // 每人最新一版是怎么问出来的
+    prompts: promptChainStats([...latest.values()].map((s) => s.id)),
   })
 })
 

server/src/services/prompt.ts

@@ -1,5 +1,6 @@
 import { all, get, run, now, newUuidHex } from "../db"
 import { Role, type User } from "../auth"
+import { pyRound } from "./pyround"
 
 export interface MessageRow {
   id: number
@@ -141,3 +142,38 @@ export function buildPromptRounds(source: MessageRow) {
   }
   return rounds
 }
+
+// 课堂总结：这些提交各自是怎么问出来的（只走覆盖索引，不读提问和代码）
+export function promptChainStats(submissionIds: string[]) {
+  type Slim = { conversation_id: string; created: string; id: number; role: string; source: string; prompt_level: number | null }
+  const finals = all<Omit<Slim, "role" | "prompt_level">>(
+    `SELECT conversation_id, created, id, source FROM prompt_message
+     WHERE submission_id IN (SELECT value FROM json_each($ids))`,
+    { ids: JSON.stringify(submissionIds) },
+  )
+  const byConv = new Map<string, Slim[]>()
+  const msgs = all<Slim>(
+    `SELECT conversation_id, created, id, role, source, prompt_level FROM prompt_message
+     WHERE conversation_id IN (SELECT value FROM json_each($convs))`,
+    { convs: JSON.stringify([...new Set(finals.map((f) => f.conversation_id))]) },
+  )
+  for (const m of msgs) byConv.set(m.conversation_id, [...(byConv.get(m.conversation_id) ?? []), m])
+
+  const out = { with_chain: finals.length, one_round: 0, external: 0, used_guidance: 0, avg_rounds: 0 }
+  const levels = [0, 0, 0, 0, 0, 0]
+  let rounds = 0
+  for (const f of finals) {
+    // 和 buildPromptRounds 一样：只算交的那一版之前的提问
+    const asked = (byConv.get(f.conversation_id) ?? []).filter(
+      (m) => m.role === "user" && (m.created < f.created || (m.created === f.created && m.id < f.id)),
+    )
+    const code = asked.filter((m) => m.source !== "guidance")
+    rounds += code.length
+    if (code.length === 1) out.one_round++
+    if (f.source === "manual") out.external++
+    if (code.length < asked.length) out.used_guidance++
+    for (const m of code) if (m.prompt_level) levels[m.prompt_level - 1]!++
+  }
+  out.avg_rounds = finals.length ? pyRound(rounds / finals.length, 1) : 0
+  return { ...out, levels }
+}

server/tests/api.test.ts

@@ -645,6 +645,39 @@ describe("课堂总结", () => {
     const all = await adm("GET", `/api/submission/stats/${task}`)
     expect(all.json.top_scored.map((t: any) => t.username)).toEqual(["weba2小李", "weba1小明"])
   })
+
+  test("统计每人最新一版的提示词链", async () => {
+    const { createConversation, insertMessage } = await import("../src/services/prompt")
+    makeUser("adm", "admin")
+    const task = makeTask("挑战")
+    const say = (conv: string, source: string, level: number | null, submission_id?: string) => {
+      const id = insertMessage({ conversation_id: conv, role: "user", source, content: "提问" })
+      run(`UPDATE prompt_message SET prompt_level = $level WHERE id = $id`, { level, id })
+      insertMessage({ conversation_id: conv, role: "assistant", source, content: "回答", submission_id })
+    }
+    // 小明：AI 对话 → 引导 → 外部 AI，交最后这版；交了之后的提问不算
+    const a = makeUser("weba1小明", "normal", "a1")
+    const convA = createConversation(a, task)
+    say(convA, "conversation", 3)
+    say(convA, "guidance", 2)
+    say(convA, "manual", 6, makeSubmission(a, task))
+    say(convA, "conversation", 1)
+    // 小红：一轮就交
+    const b = makeUser("weba1小红", "normal", "a1")
+    say(createConversation(b, task), "conversation", 1, makeSubmission(b, task))
+    // 小刚：手动交的，没有提示词
+    makeSubmission(makeUser("weba1小刚", "normal", "a1"), task)
+
+    const res = await (await client("adm"))("GET", `/api/submission/stats/${task}`)
+    expect(res.json.prompts).toEqual({
+      with_chain: 2,
+      one_round: 1,
+      external: 1,
+      used_guidance: 1,
+      avg_rounds: 1.5,
+      levels: [1, 0, 1, 0, 0, 1],
+    })
+  })
 })
 
 describe("提示词分类", () => {