feat(browser): self-heal sessions after camofox restarts (BR-3)

- Any session operation that hits 404/410 (or finds no open tab) reconciles
  tabs; if none survive it re-injects the account cookies (BR-2), opens a new
  tab under the same userId/sessionKey, returns to the recorded URL (site home
  otherwise), marks old tabs lost and retries the operation once. Failure
  returns 503 browser_reconnect_failed with the reason, with a 10s backoff.
- Restart detection: umt plugin GET /umt/instance (fallback /health fields);
  a changed instance id marks every open session needsReconnect.
- POST /browser/sessions/{id}/reconnect (idempotent); session view exposes
  needsReconnect and reconnect {status, trigger, at, reason, humanNotice}.
- Controller and lease are kept; reconnecting during takeover asks the human
  to double-check the reloaded page.
- Web: screenshot and desktop modes show "reconnecting", auto-reconnect once,
  pause polling, offer a reconnect button with the reason on failure; desktop
  mode rebuilds the Selkies connection after a reconnect.
- Mock camofox restart(), tests, smoke step and runbook section 10.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docker/browser-desktop/root/opt/camofox/plugins/umt-cookies/index.js

@@ -5,12 +5,17 @@
  * (CAMOFOX_ACCESS_KEY,ctx.auth())之下提供:
  *   POST /umt/sessions/:userId/cookies  { cookies: Cookie[] }  → 写入该 profile 的 BrowserContext 并触发持久化落盘
  *   GET  /umt/sessions/:userId/cookies?urls=a,b                → 读作用于这些地址的 Cookie(活动上下文优先,否则读落盘文件)
+ *   GET  /umt/instance                                         → { instanceId, startedAt }:插件加载时生成,进程重启即变
+ *                                                                (BR-3:app 据此发现容器重启,把会话标为需要重新连接)
  * Cookie 值只在请求/响应体里,不写日志(只记个数)。
  */
+import { randomUUID } from "node:crypto";
 import fs from "node:fs/promises";
 import express from "express";
 import { getUserPersistencePaths } from "../../lib/persistence.js";
 
+const INSTANCE = { instanceId: randomUUID(), startedAt: new Date().toISOString() };
+
 const FIELDS = ["name", "value", "domain", "path", "expires", "httpOnly", "secure", "sameSite"];
 
 function parseUrls(raw) {
@@ -101,5 +106,7 @@ export async function register(app, ctx) {
     }
   });
 
-  log("info", "umt-cookies plugin: registered GET/POST /umt/sessions/:userId/cookies");
+  app.get("/umt/instance", ctx.auth(), (_req, res) => res.json(INSTANCE));
+
+  log("info", "umt-cookies plugin: registered GET/POST /umt/sessions/:userId/cookies, GET /umt/instance");
 }