feat(flow): 链路图本地落盘 + 多轮历史回放（design/19 §P3，契约 v0.73）

主人要求「链路流程应该有本地数据，不然每次重载之后页面就没数据了」：
- 落盘：迁移 0022_flow_graphs（session_id/turn_id/graph_json/时间戳 + 唯一键 upsert）+ internal/runtime/flowgraph（RecordRound/Graph/Latest/Turns/Turn + 保留期 GC）
- 写入：loop.EndRound **每轮一条**（锁外深拷贝后写；失败 WARN 且不打印图内容）；只落发布会话白名单（复用 flowSessionAllowed）
- 读回：端点加 turnId + source(live/persisted/none) + turns[]（最新在前，空为 []）；**内存优先、miss 才落盘**（最新一轮永远最新）
- 前端：flowGraphs 纳入 persistOptions.partialize（**刷新即刻有图**，version 3→4 + migrate）+ 历史轮选择器 + 诚实文案；顺带收 L1 转交的 flow/NodeDetail.tsx 节点日志倒序
- 新 env 键：FLOW_GRAPH_RETENTION=168h / FLOW_GRAPH_GC_INTERVAL=1h
- 变异实测：每 span 一行 / 保留期守卫失效 / partialize 去掉 flowGraphs / 去掉内存优先 / 白名单失效 ⇒ 全部打红
- 3 个禁动面文件的纯追加改动（Flow.tsx 挂选择器、FlowSnapshotHint 纠已成假话的文案、其渲染断言随之更新）由主会话裁定认可
- 登记存疑：图桶持久化无体积上限；useFlowTurns 的 effect 无自动化证据（项目无 jsdom）

frontend/web/src/store/persistOptions.test.ts

@@ -0,0 +1,72 @@
+// 前端 store 持久化的**纯逻辑**测试（切片 F2；主人要求「每次重载之后页面就没数据」）。
+//
+// 只钉一件事：`flowGraphs`（按会话分的链路图桶）**必须**在 zustand persist 的
+// `partialize` 里 —— 否则刷新页面时图桶被抹掉，「刷新即刻有图」就不成立。同时钉住
+// `migrate` 对旧版本（v3 之前没有图桶）给出空桶默认。
+//
+// 跑法：
+//
+//   cd frontend/web \
+//     && ./node_modules/.bin/esbuild src/store/persistOptions.test.ts \
+//          --bundle --platform=node --format=esm \
+//          --outfile=/tmp/cyrene-persist-options.test.mjs \
+//     && node /tmp/cyrene-persist-options.test.mjs
+//
+// `tsc --noEmit` 会对本文件做类型检查，因此它不 import node:*；只类型引入 AppStore
+// （编译后被擦除，不触发 useAppStore 的运行时副作用）。
+
+import type { AppStore } from "./useAppStore";
+import type { FlowGraph } from "../lib/types";
+import { persistOptions } from "./persistOptions";
+
+let checks = 0;
+
+function ok(cond: boolean, what: string): void {
+  checks += 1;
+  if (!cond) throw new Error(`FAILED: ${what}`);
+}
+
+function same<T>(got: T, want: T, what: string): void {
+  checks += 1;
+  if (got !== want) throw new Error(`FAILED: ${what} — got ${String(got)}, want ${String(want)}`);
+}
+
+const graph: FlowGraph = {
+  id: "web-1",
+  sessionId: "web",
+  nodes: [{ id: "input", label: "你好", kind: "input", status: "done" }],
+  edges: [],
+};
+
+const state = {
+  activeSessionId: "web",
+  sessions: { web: { id: "web" } },
+  personas: [],
+  moods: { cyrene: "开心" },
+  context: {},
+  backthink: [],
+  flowGraphs: { web: graph },
+} as unknown as AppStore;
+
+// ── ① partialize 必须含 flowGraphs（刷新即刻有图的内核） ─────────────────────
+const persisted = persistOptions.partialize(state) as unknown as Record<string, unknown>;
+ok("flowGraphs" in persisted, "partialize 必须包含 flowGraphs —— 否则刷新后图桶被抹掉");
+same(persisted.flowGraphs, state.flowGraphs, "持久化的图桶必须是当前 store 里的那份");
+
+// ── ② 版本号已升到 4（v3 之前没有图桶，迁移时必须补空桶） ─────────────────────
+same(persistOptions.version, 4, "引入 flowGraphs 持久化后版本应为 4");
+
+// ── ③ migrate：旧版本（没有图桶）⇒ 补一个空桶；已存在的桶保留 ────────────────
+const migratedOld = persistOptions.migrate({}, 3) as unknown as Record<string, unknown>;
+same(JSON.stringify(migratedOld.flowGraphs), "{}", "v3 旧状态迁移后图桶是空对象（随后由快照补）");
+
+const migratedKeep = persistOptions.migrate({ flowGraphs: { web: graph } }, 3) as unknown as Record<
+  string,
+  unknown
+>;
+ok(
+  (migratedKeep.flowGraphs as Record<string, FlowGraph>).web?.id === "web-1",
+  "迁移必须保留已有的图桶"
+);
+
+console.log(`persist options test: ${checks} checks passed`);

frontend/web/src/store/persistOptions.ts

@@ -10,7 +10,7 @@ import type { AppStore } from "./useAppStore";
  */
 export const persistOptions = {
   name: "cyrene.app",
-  version: 3,
+  version: 4,
   // v1 persisted the whole chat (`messages` + a single `sessionId`); v2 added
   // one resolved `currentPersona`, which can no longer describe the active role
   // now that the role belongs to a *session*. Both shapes are dropped:
@@ -18,6 +18,8 @@ export const persistOptions = {
   // the session list. `moods` is transient by nature (a restart resets a role's
   // mood), so it is not carried across either. A v1 state was never trusted for
   // the session metadata, so those users simply restart on the main session.
+  // v4 (切片 F2) added `flowGraphs` (the per-session flow-graph buckets): a v3
+  // state has none, so it starts empty and is refilled by the snapshot hook.
   migrate: (persisted: unknown, version: number) => {
     const p = (persisted ?? {}) as Partial<AppStore>;
     const fromV1 = version < 2;
@@ -28,6 +30,7 @@ export const persistOptions = {
       moods: {},
       context: p.context ?? {},
       backthink: p.backthink ?? [],
+      flowGraphs: p.flowGraphs ?? {},
     };
   },
   partialize: (s: AppStore) => ({
@@ -43,5 +46,11 @@ export const persistOptions = {
     moods: s.moods,
     context: s.context,
     backthink: s.backthink,
+    // v4 (切片 F2): the per-session flow-graph buckets are persisted too, so a
+    // refresh paints the last-seen graph immediately instead of flashing the
+    // empty state until the snapshot fetch returns (主人 2026-10-05「每次重载
+    // 之后页面就没数据了」). Bounded by `MAX_GRAPHS` (store/sessionCache.ts);
+    // the backend stays the truth and the snapshot/history endpoints refill it.
+    flowGraphs: s.flowGraphs,
   }),
 };