docs: SPA 管理凭据 trust-root 同步（README/zh-CN/reference 三处措辞 + 锚点修正）

承接 800d6e0（SPA 凭据改用 CONFIG_ENCRYPTION_KEY）：

- README.md §5、README.zh-CN.md §5：trust-root 段落补齐「配置密钥即管理密钥」
  的事实陈述，消除「Redis ACL 密码」的残留耦合叙述。
- docs/reference.md §3 Trust root：1:1 重写为配置密钥派生路径，移除不存在的
  "refresh loop" 叙述（实际为 refresh_business_config 单次调用 + guard）。
- docs/reference.md §3 锚点修正：expires_in 引用 notify.rs:700→:787
  （refresh_business_config 现位于 :717，expires_in 在 :787）。

交付方：文件规划助手（任务 01a0e379）。文档校验器 0 error，负向对照 4/4。

README.md

@@ -81,9 +81,11 @@ that must stay cheap should watch the gateway's aggregated `/healthz`.
 > All state lives in Redis; the process reads only two environment variables and writes
 > nothing to disk.
 
-One corollary matters for setup: the bootstrap one-shot token is the **password component of
-`REDIS_URL`**. The Redis ACL credential is therefore both the application connection
-credential and the trust root for bootstrap — keep it private and rotate it as one value.
+One corollary matters for setup: the SPA admin credential — and therefore the bootstrap
+trust root — is `CONFIG_ENCRYPTION_KEY` itself, the single 32-byte hex value you supply at
+startup. It is only compared in constant time, and is never echoed, logged, or stored. The
+Redis ACL password, if you have one, authenticates the Redis connection alone and is not
+the credential for any HTTP endpoint.
 
 ## 5. Where to read more
 

README.zh-CN.md

@@ -74,8 +74,7 @@ docker run --env-file .env -p 8080:8080 messageweave:latest
 
 > 所有状态都在 Redis 里；进程只读两个环境变量，不写任何磁盘。
 
-有一条推论与部署直接相关：bootstrap 的一次性 token 就是 **`REDIS_URL` 的密码分量**。因此
-Redis ACL 凭据同时是应用连接凭据与 bootstrap 信任根——请单独保管并按单一值轮换。
+有一条推论与部署直接相关：SPA 管理凭据——也就是 bootstrap 的信任根——就是 `CONFIG_ENCRYPTION_KEY` 本身，即启动时提供的那个 32 字节 hex 值。它只做常数时间比较，绝不回显、记录或落盘。Redis ACL 密码（如有）只认证 Redis 连接本身，不是任何 HTTP 端点的认证凭据。
 
 ## 5. 去哪读更多
 

docs/reference.md

@@ -34,13 +34,14 @@ Conventions used throughout:
 
 Notes:
 
-- `config:business:revision` is an **atomic Redis `INCR`**, not a read-modify-write. Hot reload
-  compares it: the refresh loop only rebuilds the worker when the remote revision exceeds the
-  cached local value, which is what keeps a single bad poll from turning into a hot retry loop
-  (notify.rs:627-650).
+- `config:business:revision` is an **atomic Redis `INCR`**, not a read-modify-write. Every
+  request-bearing entry point calls `refresh_business_config` (notify.rs:717), which only
+  rebuilds the worker when the remote revision exceeds the cached local value
+  (notify.rs:722-724) — that guard is what keeps a stale or malformed snapshot from turning
+  into a rebuild loop.
 - `config:admin_session` carries no TTL metadata beyond the literal `EX 900` passed at write
   time; the handler reports the same window in its response body as `expires_in: 900`
-  (notify.rs:700).
+  (notify.rs:787).
 - `config:enabled` is consulted as a gate; missing or `false` keeps business processing off.
 
 ### 1.2 AI consent
@@ -310,9 +311,16 @@ compatibility. Recognised names, unprefixed unless noted:
 The single prefixed name is `TELEGRAM_CHAT_ID`. Anything else documented as
 `TELEGRAM_BOT_TOKEN` or similar is a documentation error, not a supported variable.
 
-**Trust root.** The bootstrap one-shot token is the password component of `REDIS_URL`
-(main.rs:87-91). The Redis ACL credential is therefore simultaneously the application
-connection credential and the trust root for bootstrap.
+**Trust root.** The SPA admin credential is `CONFIG_ENCRYPTION_KEY` itself: read at startup
+(main.rs:49) and held as `admin_token` (main.rs:95), it is checked in constant time by
+`worker_authorized` (notify.rs:445; compare at notify.rs:1135) at the top of both
+`POST /api/bootstrap` (notify.rs:604) and `POST /api/admin/session` (notify.rs:774). It is
+only compared against the request bearer — never echoed, logged, or stored. The session
+issued by `/api/admin/session` is a freshly generated random 32-byte hex token
+(notify.rs:778-787), never the credential; only its digest is retained in Redis under
+`config:admin_session`. `REDIS_URL` is the Redis connection string alone: an ACL password in
+it, if any, authenticates the Redis connection and is not the credential for any HTTP
+endpoint.
 
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