feat(xiaomi-mimo): server-assisted desktop login, five account clusters, v2.6 models

Reproduce the MiMo Desktop login surface server-side so headless/Docker
deployments can link a Xiaomi account without the Desktop client. The
account session (passToken) is captured during the proxied login and
stored per connection.

- Five account clusters (cn/sgp/ams/ru/in): per-region mimo-server host
  and SSO sid, unknown region falls back to sgp
- mimo-v2.6-pro/flash/pro-ultraspeed dual-route models: account-service
  route when desktop credentials exist, cloud API (sk- key) otherwise;
  drops obsolete mimo-x-*-preview ids
- Desktop ServiceTokenManager 2-phase handshake (single serviceLogin with
  target sid, raw 64-bit nonce preserved), per-region session cache
- reasoning_effort bridged to output_config.effort; i18n runtime now
  observes characterData mutations so React text rewrites get translated
- Security hardening on the login proxy: session travels only in the
  httpOnly cookie (never in the URL), proxy branch requires dashboard
  auth, authorization/proxy-authorization never forwarded upstream, and
  upstream Set-Cookie is not replayed onto the app origin

open-sse/providers/thinkingLevels.js

@@ -41,6 +41,7 @@ const PATTERN_THINKING = [
   { provider: "codex", pattern: "*gpt-5.6-terra*", levels: [...CODEX_GPT_5_6_LEVELS, "ultra"] },
   { provider: "codex", pattern: "*gpt-5.6-luna*", levels: CODEX_GPT_5_6_LEVELS },
   { pattern: "*codex*", levels: ["low", "medium", "high", "xhigh"] }, // codex cannot disable thinking
+  { pattern: "*mimo*v2.6*", levels: ["none", "low", "medium", "high", "xhigh"] },
   // DeepSeek v4.* (Alibaba MaaS, probed live): effort low|medium|high|xhigh|max
   // all 200 via output_config.effort; "none" is a 400 on the anthropic route
   // (disable thinking instead). none kept for the picker = disable.