docs: remove unnecessary RUN_MODE mentions from README and reference

The sentence explained why RUN_MODE doesn't exist — but if it doesn't
exist, there's nothing to explain. Removed from README (EN+ZH) §4 and
reference (EN+ZH) §5.1. Also fixed Chinese curly quotes to backticks
on the DEBUG_TOKEN row in reference.zh-CN.md §5.1.

README.md

@@ -281,8 +281,6 @@ Three layers. They are not interchangeable.
 | `CONFIG_ENCRYPTION_KEY` | yes | — |
 | `PORT` | no | `8080` |
 
-There is no `RUN_MODE`: the legacy environment parser was removed, and webhook plus
-reconcile traffic share one router (`POST /reconcile` is a standalone endpoint).
 `.env.example` ships only the two required
 variables; the rest are documented defaults.
 

README.zh-CN.md

@@ -197,7 +197,7 @@ scripts/cron-drain.sh
 | `CONFIG_ENCRYPTION_KEY` | 是 | — |
 | `PORT` | 否 | `8080` |
 
-没有 `RUN_MODE`：遗留的环境变量解析器已删除，webhook 与 reconcile 流量共享同一套路由表（`POST /reconcile` 是独立端点）。`.env.example` 只提供 2 个必需变量；其余是
+`.env.example` 只提供 2 个必需变量；其余是
 文档化默认值。
 
 **业务配置 —— 存于 Redis，由浏览器写入。**

docs/reference.md

@@ -359,11 +359,6 @@ Three distinct layers. They are not interchangeable.
 | `DEBUG_ENABLED` | no | — | truthy values are `1`/`true`/`TRUE`/`True`/`yes`/`YES` (exact match); enables the debug surface on its own, paired with `--debug` as an alternative (`SAF-DEBUG-GATE`) |
 | `DEBUG_TOKEN` | no | — | effective only once the debug surface is requested via `DEBUG_ENABLED` or `--debug` (`SAF-DEBUG-GATE` / `SAF-DEBUG-ORIGIN-ONLY`) |
 
-`RUN_MODE` **no longer exists**: the identifier was removed together with the legacy
-`Config::from_env()` environment parser (registration in `docs/retired.md`). Both webhook
-and reconcile traffic share one router and reconcile is a standalone `POST /reconcile`
-endpoint, so the variable never changed any runtime behaviour — there is now nothing to set.
-
 **Missing a required variable does not crash the process.** It logs a warning and serves
 `router_configuration_setup`, which mounts only `/api/status`,
 `/ready` and `/healthz` on top of the static SPA. The business and admin routes from §3 are not

docs/reference.zh-CN.md

@@ -348,12 +348,7 @@ SPA 的首次启动流程仍然无法通过 Worker 的 `/api/bootstrap` 完成
 | `CONFIG_ENCRYPTION_KEY` |是的 | — | `encryption_key_from_env` |
 | `端口` |没有| `8080` | `unwrap_or(8080_u16)`。监听者直接绑定它； `Config` 不携带端口字段 |
 | `DEBUG_ENABLED` |没有| — |真值为 `1`/`true`/`TRUE`/`True`/`yes`/`YES` （完全匹配）；单独启用调试界面，与 `--debug` 配对作为替代方案 (`SAF-DEBUG-GATE`) |
-| `DEBUG_TOKEN` |没有| — |仅在通过“DEBUG_ENABLED”或“--debug”（“SAF-DEBUG-GATE”/“SAF-DEBUG-ORIGIN-ONLY”）请求调试表面后才有效
-
-`RUN_MODE` **不再存在**：标识符与旧版本一起被删除
-`Config::from_env()` 环境解析器（在 `docs/retired.md` 中注册）。两个网络钩子
-和协调流量共享一个路由器，并且协调是一个独立的“POST /reconcile”
-端点，因此该变量从未改变任何运行时行为 - 现在无需设置任何内容。
+| `DEBUG_TOKEN` |没有| — |仅在通过 `DEBUG_ENABLED` 或 `--debug`（`SAF-DEBUG-GATE`/`SAF-DEBUG-ORIGIN-ONLY`）请求调试表面后才有效
 
 **缺少必需的变量不会使进程崩溃。**它会记录警告并提供服务
 `router_configuration_setup`，仅挂载`/api/status`，